采用能量为1 Me V的电子对几种不同结构的Al Ga N/Ga N HEMT器件进行了最高注量为8.575×1014cm-2的辐照。实验发现:电子辐照后,最高注量下器件欧姆接触性能也几乎没有退化。辐照后未钝化器件的正反向栅电流有所增加,而且肖特基势...采用能量为1 Me V的电子对几种不同结构的Al Ga N/Ga N HEMT器件进行了最高注量为8.575×1014cm-2的辐照。实验发现:电子辐照后,最高注量下器件欧姆接触性能也几乎没有退化。辐照后未钝化器件的正反向栅电流有所增加,而且肖特基势垒高度随着辐照注量的增加而降低。几种结构HEMT器件的辐照结果表明,电子辐照后只有未钝化器件的特性有所退化,随着辐照注量增加,器件漏电流和跨导下降越明显,而且线性区退化大于饱和区,而阈值电压变化很小。分析表明,HEMT器件参数性能退化的主要原因是栅源和栅漏间隔区辐照感生表面态负电荷的产生。此外实验结果也说明Si N钝化、MOS结构和场板结构都是很好的抗辐照加固的手段。展开更多
采用归一化能量1 Me V的中子脉冲反应堆对Al Ga N/Ga N异质结材料进行了辐照研究。实验发现,经1015cm-2注量的中子辐照后,异质结材料的二维电子气(2DEG)载流子浓度(ns)下降,而2DEG迁移率由于受到ns的调制作用略有增加,同时辐照导致的载...采用归一化能量1 Me V的中子脉冲反应堆对Al Ga N/Ga N异质结材料进行了辐照研究。实验发现,经1015cm-2注量的中子辐照后,异质结材料的二维电子气(2DEG)载流子浓度(ns)下降,而2DEG迁移率由于受到ns的调制作用略有增加,同时辐照导致的载流子浓度ns下降造成了沟道串联电阻的增加和异质结构阈值电压(VTH)的正向漂移。分析认为,辐照感生类受主缺陷是造成ns下降和阈值电压漂移的原因。原子力显微镜(AFM)和X射线衍射仪(XRD)的测试结果表明,辐照后材料的表面形貌有所恶化,材料应变基本不变,而材料的螺位错和刃位错密度辐照后都略有增加。此外,实验结果还表明初始材料质量越好,辐照退化越小。展开更多
Al0.2Ga0.8N/GaN/Al_(0.2)Ga_(0.8)N multilayer structures and GaN monolayer structures with AIN as the buffer layers were grown on Si substrates by metal-organic chemical vapour deposition. The photocurrent responses of...Al0.2Ga0.8N/GaN/Al_(0.2)Ga_(0.8)N multilayer structures and GaN monolayer structures with AIN as the buffer layers were grown on Si substrates by metal-organic chemical vapour deposition. The photocurrent responses of these structures were measured and analysed. The multilayer structures showed a high response in a narrow range of wavelengths. The peak wavelength is located at 365 nm at which the responsivity is as high as 24 A/W under 5.5 V bias;this is much higher than the GaN monolayer structure. This high responsivity results mainly from the high polarization electric field in the GaN layer of the Al_(0.2)Ga_(0.8)N/GaN/Al_(0.2)Ga_(0.8)N heterostructure.展开更多
In the magnetotransport measurements of the two-dimensional electron gas (2DEG) in modulation-doped Al_(0.22)Ga_(0.7)sN/C heterostructures, a new magnetoresistance oscillation of the 2DEG is observed at low magnetic f...In the magnetotransport measurements of the two-dimensional electron gas (2DEG) in modulation-doped Al_(0.22)Ga_(0.7)sN/C heterostructures, a new magnetoresistance oscillation of the 2DEG is observed at low magnetic fields when the Al_(0.22)Ga_(0.7)sN layer on GaN is partially relaxed. It is thought that the misfit dislocations induced by the partially relaxed Al_(0.22)Ga_(0.7)sN layer modulate the distribution of the piezoelectric polarization-induced charges at the Al0.22Ga0.7sN/GaN heterointerface, and thus produce a strong modulation potential at the heterointerface. The strong modulation potential results in the novel magnetoresistance oscillation of the 2DEG at low magnetic fields.展开更多
Structural properties of InxGa_(1−x)N/GaN multi-quantum wells(MQWs)grown on sapphire by metal organic chemical vapor deposition are investigated by synchrotron radiation x-ray diffraction(SRXRD),Rutherford backscatter...Structural properties of InxGa_(1−x)N/GaN multi-quantum wells(MQWs)grown on sapphire by metal organic chemical vapor deposition are investigated by synchrotron radiation x-ray diffraction(SRXRD),Rutherford backscattering/channelling(RBS/C)and high-resolution transmission electron microscopy.The sample consists of eight periods of InxGa_(1−x)N/GaN wells of 2.1 nm thickness and 8.5 nm thickness of GaN barrier,and the results are very close,which verifies the accuracy of the three methods.The indium content in InxGa_(1−x)N/GaN MQWs by SRXRD and RBS/C is estimated,and results are in general the same.By RBS/C random spectra,the indium atomic lattice substitution rate is 94.0%,indicating that almost all indium atoms in InxGa_(1−x)N/GaN MQWs are at substitution,that the indium distribution of each layer in InxGa_(1−x)N/GaN MQWs is very homogeneous and that the InxGa_(1−x)N/GaN MQWs have a very good crystalline quality.It is not accurate to estimate indium content in InxGa_(1−x)N/GaN MQWs by photoluminescence(PL)spectra,because the result from the PL experimental method is very different from the results by the SRXRD and RBS/C experimental methods.展开更多
The modulation-doped Al_(0.22)Ga_(0.78)N/GaN heterostructures with different Al_(0.22)Ga_(0.78)N barrier thicknesses were grown by means of metal--organic chemical vapour deposition.The Al_(0.22)Ga_(0.78)N layer still...The modulation-doped Al_(0.22)Ga_(0.78)N/GaN heterostructures with different Al_(0.22)Ga_(0.78)N barrier thicknesses were grown by means of metal--organic chemical vapour deposition.The Al_(0.22)Ga_(0.78)N layer still has pseudomorphic growth when its thickness is 53nm.The mobility of the two-dimensional electron gas(2DEG)at the heterointerfaces is much higher than that of the electrons in GaN films at both 300 and 77K.The dramatic decrease of the 2DEG mobility in an Al_(0.22)Ga_(0.78)N/GaN heterostructure corresponds to the partial relaxation of the Al_(0.22)Ga_(0.78)N barrier.展开更多
Low-field magnetotransport properties of two-dimensional electron gases(2DEGs)are investigated in Al_(0.22)Ga_(0.78)N/GaN heterostructures.By means of a tilting magnetic field,unexpected oscillations of magnetoresisti...Low-field magnetotransport properties of two-dimensional electron gases(2DEGs)are investigated in Al_(0.22)Ga_(0.78)N/GaN heterostructures.By means of a tilting magnetic field,unexpected oscillations of magnetoresistivity are observed in a weak localization region.Qualitative understanding based on Altshuler–Aronov–Spivak oscillations is proposed for the case of interface disorder in Al_(0.22)Ga_(0.78)N/GaN heterostructures.展开更多
The valence band offset(VBO)of an Al_(0.17)Ga_(0.83)N/GaN heterojunction is determined to be 0.13±0.07 eV by x-ray photoelectron spectroscopy.From the obtained VBO value,the conduction band offset(CBO)of~0.22 eV ...The valence band offset(VBO)of an Al_(0.17)Ga_(0.83)N/GaN heterojunction is determined to be 0.13±0.07 eV by x-ray photoelectron spectroscopy.From the obtained VBO value,the conduction band offset(CBO)of~0.22 eV is obtained.The results indicate that the Al_(0.17)Ga_(0.83)N/GaN heterojunction exhibits a type-Ⅰ band alignment.展开更多
In this study, we investigate the effects of Ga N cap layer thickness on the two-dimensional electron gas（2DEG）electron density and 2DEG electron mobility of Al N/Ga N heterostructures by using the temperature-depen...In this study, we investigate the effects of Ga N cap layer thickness on the two-dimensional electron gas（2DEG）electron density and 2DEG electron mobility of Al N/Ga N heterostructures by using the temperature-dependent Hall measurement and theoretical fitting method. The results of our analysis clearly indicate that the Ga N cap layer thickness of an Al N/Ga N heterostructure has influences on the 2DEG electron density and the electron mobility. For the Al N/Ga N heterostructures with a 3-nm Al N barrier layer, the optimized thickness of the Ga N cap layer is around 4 nm and the strained a-axis lattice constant of the Al N barrier layer is less than that of Ga N.展开更多
The parasitic source resistance（RS） of AlGaN/AlN/GaN heterostructure field-effect transistors（HFETs） is studied in the temperature range 300–500 K. By using the measured RSand both capacitance–voltage（C–V） an...The parasitic source resistance（RS） of AlGaN/AlN/GaN heterostructure field-effect transistors（HFETs） is studied in the temperature range 300–500 K. By using the measured RSand both capacitance–voltage（C–V） and current–voltage（I–V） characteristics for the fabricated device at 300, 350, 400, 450, and 500 K, it is found that the polarization Coulomb field（PCF） scattering exhibits a significant impact on RSat the above-mentioned different temperatures. Furthermore, in the AlGaN/AlN/GaN HFETs, the interaction between the additional positive polarization charges underneath the gate contact and the additional negative polarization charges near the source Ohmic contact, which is related to the PCF scattering, is verified during the variable-temperature study of RS.展开更多
Ni/Au Schottky contacts on AlN/GaN and AlGaN/GaN heterostructures are fabricated. Based on the measured current-voltage and capacitance-voltage curves, the polarization sheet charge density and relative permittivity a...Ni/Au Schottky contacts on AlN/GaN and AlGaN/GaN heterostructures are fabricated. Based on the measured current-voltage and capacitance-voltage curves, the polarization sheet charge density and relative permittivity are analyzed and calculated by self-consistently solving Schrodinger＇s and Poisson＇s equations. It is found that the values of relative permittivity and polarization sheet charge density of AlN/GaN diode are both much smaller than the ones of AlGaN/GaN diode, and also much lower than the theoretical values. Moreover, by fitting the measured forward 1-V curves, the extracted dislocations existing in the barrier layer of the AlN/GaN diode are found to be much more than those of the AlGaN/GaN diode. As a result, the conclusion can be made that compared with AlGaN/GaN diode the Schottky metal has an enhanced influence on the strain of the extremely thinner AlN barrier layer, which is attributed to the more dislocations.展开更多
Ni/Au Schottky contacts on A1N/GaN and A1GaN/GaN heterostructures are fabricated. Based on the measured current-voltage and capacitance-voltage curves, the electrical characteristics of AlN/GaN Schottky diode, such as...Ni/Au Schottky contacts on A1N/GaN and A1GaN/GaN heterostructures are fabricated. Based on the measured current-voltage and capacitance-voltage curves, the electrical characteristics of AlN/GaN Schottky diode, such as Schottky barrier height, turn-on voltage, reverse breakdown voltage, ideal factor, and the current-transport mechanism, are analyzed and then compared with those of an A1GaN/GaN diode by self-consistently solving Schrodinger＇s and Poisson＇s equations. It is found that the dislocation-governed tunneling is dominant for both AlN/GaN and AlGaN/GaN Schottky diodes. However, more dislocation defects and a thinner barrier layer for AlN/GaN heterostrncture results in a larger tunneling probability, and causes a larger leakage current and lower reverse breakdown voltage, even though the Schottky barrier height of AlN/GaN Schottky diode is calculated to be higher that of an A1GaN/GaN diode.展开更多
High-performance Al Ga N/Ga N high electron mobility transistors（HEMTs） grown on silicon substrates by metal–organic chemical-vapor deposition（MOCVD） with a selective non-planar n-type Ga N source/drain（S/D） re...High-performance Al Ga N/Ga N high electron mobility transistors（HEMTs） grown on silicon substrates by metal–organic chemical-vapor deposition（MOCVD） with a selective non-planar n-type Ga N source/drain（S/D） regrowth are reported. A device exhibited a non-alloyed Ohmic contact resistance of 0.209 Ω·mm and a comprehensive transconductance（gm） of 247 m S/mm. The current gain cutoff frequency f T and maximum oscillation frequency f MAX of 100-nm HEMT with S/D regrowth were measured to be 65 GHz and 69 GHz. Compared with those of the standard Ga N HEMT on silicon substrate, the fTand fMAXis 50% and 52% higher, respectively.展开更多
文摘采用能量为1 Me V的电子对几种不同结构的Al Ga N/Ga N HEMT器件进行了最高注量为8.575×1014cm-2的辐照。实验发现:电子辐照后,最高注量下器件欧姆接触性能也几乎没有退化。辐照后未钝化器件的正反向栅电流有所增加,而且肖特基势垒高度随着辐照注量的增加而降低。几种结构HEMT器件的辐照结果表明,电子辐照后只有未钝化器件的特性有所退化,随着辐照注量增加,器件漏电流和跨导下降越明显,而且线性区退化大于饱和区,而阈值电压变化很小。分析表明,HEMT器件参数性能退化的主要原因是栅源和栅漏间隔区辐照感生表面态负电荷的产生。此外实验结果也说明Si N钝化、MOS结构和场板结构都是很好的抗辐照加固的手段。
文摘采用归一化能量1 Me V的中子脉冲反应堆对Al Ga N/Ga N异质结材料进行了辐照研究。实验发现,经1015cm-2注量的中子辐照后,异质结材料的二维电子气(2DEG)载流子浓度(ns)下降,而2DEG迁移率由于受到ns的调制作用略有增加,同时辐照导致的载流子浓度ns下降造成了沟道串联电阻的增加和异质结构阈值电压(VTH)的正向漂移。分析认为,辐照感生类受主缺陷是造成ns下降和阈值电压漂移的原因。原子力显微镜(AFM)和X射线衍射仪(XRD)的测试结果表明,辐照后材料的表面形貌有所恶化,材料应变基本不变,而材料的螺位错和刃位错密度辐照后都略有增加。此外,实验结果还表明初始材料质量越好,辐照退化越小。
基金Supported by the Special Funds for Major State Basic Research Project of China No.G20000683the National Natural Science Foundation of China under Grant Nos.69987001,69636010,69976014,69806006。
文摘Al0.2Ga0.8N/GaN/Al_(0.2)Ga_(0.8)N multilayer structures and GaN monolayer structures with AIN as the buffer layers were grown on Si substrates by metal-organic chemical vapour deposition. The photocurrent responses of these structures were measured and analysed. The multilayer structures showed a high response in a narrow range of wavelengths. The peak wavelength is located at 365 nm at which the responsivity is as high as 24 A/W under 5.5 V bias;this is much higher than the GaN monolayer structure. This high responsivity results mainly from the high polarization electric field in the GaN layer of the Al_(0.2)Ga_(0.8)N/GaN/Al_(0.2)Ga_(0.8)N heterostructure.
基金Supported by the Special Funds for Major State Basic Research Projects of China(G20000683)the National Natural Science Foundation of China under Grant Nos.69806006,69976014,and 69987001the National High Technology Research&Development Project of China.
文摘In the magnetotransport measurements of the two-dimensional electron gas (2DEG) in modulation-doped Al_(0.22)Ga_(0.7)sN/C heterostructures, a new magnetoresistance oscillation of the 2DEG is observed at low magnetic fields when the Al_(0.22)Ga_(0.7)sN layer on GaN is partially relaxed. It is thought that the misfit dislocations induced by the partially relaxed Al_(0.22)Ga_(0.7)sN layer modulate the distribution of the piezoelectric polarization-induced charges at the Al0.22Ga0.7sN/GaN heterointerface, and thus produce a strong modulation potential at the heterointerface. The strong modulation potential results in the novel magnetoresistance oscillation of the 2DEG at low magnetic fields.
基金by the National Natural Science Foundation of China under Grant No 10875004 and 11005005the National Basic Research Program of China under Grant No 2010CB832904.
文摘Structural properties of InxGa_(1−x)N/GaN multi-quantum wells(MQWs)grown on sapphire by metal organic chemical vapor deposition are investigated by synchrotron radiation x-ray diffraction(SRXRD),Rutherford backscattering/channelling(RBS/C)and high-resolution transmission electron microscopy.The sample consists of eight periods of InxGa_(1−x)N/GaN wells of 2.1 nm thickness and 8.5 nm thickness of GaN barrier,and the results are very close,which verifies the accuracy of the three methods.The indium content in InxGa_(1−x)N/GaN MQWs by SRXRD and RBS/C is estimated,and results are in general the same.By RBS/C random spectra,the indium atomic lattice substitution rate is 94.0%,indicating that almost all indium atoms in InxGa_(1−x)N/GaN MQWs are at substitution,that the indium distribution of each layer in InxGa_(1−x)N/GaN MQWs is very homogeneous and that the InxGa_(1−x)N/GaN MQWs have a very good crystalline quality.It is not accurate to estimate indium content in InxGa_(1−x)N/GaN MQWs by photoluminescence(PL)spectra,because the result from the PL experimental method is very different from the results by the SRXRD and RBS/C experimental methods.
基金Supported by the National Natural Science Foundation of China under Grant Nos.69806006,69636010,69976017 and 69987001the National High Technology Research&Development Project of China(No.863-715-011-0030)+1 种基金the Research for the Future Program of the Japan Society for the Promotion of Science(Project No.JSPS-RFTF96P00201)the Foundation for the Promotion of Industrial Science in Japan.
文摘The modulation-doped Al_(0.22)Ga_(0.78)N/GaN heterostructures with different Al_(0.22)Ga_(0.78)N barrier thicknesses were grown by means of metal--organic chemical vapour deposition.The Al_(0.22)Ga_(0.78)N layer still has pseudomorphic growth when its thickness is 53nm.The mobility of the two-dimensional electron gas(2DEG)at the heterointerfaces is much higher than that of the electrons in GaN films at both 300 and 77K.The dramatic decrease of the 2DEG mobility in an Al_(0.22)Ga_(0.78)N/GaN heterostructure corresponds to the partial relaxation of the Al_(0.22)Ga_(0.78)N barrier.
基金by the National Natural Science Foundation of China under Grant Nos 60806042,10774001 and 60990313the Research Fund for the Doctoral Program of Higher Education in China(200800011021)the Wuhan National High Magnetic Field Center(WHMFCKF2011004).
文摘Low-field magnetotransport properties of two-dimensional electron gases(2DEGs)are investigated in Al_(0.22)Ga_(0.78)N/GaN heterostructures.By means of a tilting magnetic field,unexpected oscillations of magnetoresistivity are observed in a weak localization region.Qualitative understanding based on Altshuler–Aronov–Spivak oscillations is proposed for the case of interface disorder in Al_(0.22)Ga_(0.78)N/GaN heterostructures.
基金the Knowledge Innovation Program of the Chinese Academy of Sciences under Grant No YYY-0701-02the National Natural Science Foundation of China under Grant Nos 60890193 and 61106014+2 种基金the National Basic Research Program of China under Grant Nos 2010CB327503 and 2012CB619303the High-Technology Research and Development Program of China under Grant No 2011AA050514the National Science and Technology Major Project of China。
文摘The valence band offset(VBO)of an Al_(0.17)Ga_(0.83)N/GaN heterojunction is determined to be 0.13±0.07 eV by x-ray photoelectron spectroscopy.From the obtained VBO value,the conduction band offset(CBO)of~0.22 eV is obtained.The results indicate that the Al_(0.17)Ga_(0.83)N/GaN heterojunction exhibits a type-Ⅰ band alignment.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11174182 and 61306113)the Specialized Research Fund for the Doctoral Program of Higher Education,China(Grant No.20110131110005)
文摘In this study, we investigate the effects of Ga N cap layer thickness on the two-dimensional electron gas（2DEG）electron density and 2DEG electron mobility of Al N/Ga N heterostructures by using the temperature-dependent Hall measurement and theoretical fitting method. The results of our analysis clearly indicate that the Ga N cap layer thickness of an Al N/Ga N heterostructure has influences on the 2DEG electron density and the electron mobility. For the Al N/Ga N heterostructures with a 3-nm Al N barrier layer, the optimized thickness of the Ga N cap layer is around 4 nm and the strained a-axis lattice constant of the Al N barrier layer is less than that of Ga N.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11174182,11574182,and 61306113)the Specialized Research Fund for the Doctoral Program of Higher Education of China(Grant No.20110131110005)
文摘The parasitic source resistance（RS） of AlGaN/AlN/GaN heterostructure field-effect transistors（HFETs） is studied in the temperature range 300–500 K. By using the measured RSand both capacitance–voltage（C–V） and current–voltage（I–V） characteristics for the fabricated device at 300, 350, 400, 450, and 500 K, it is found that the polarization Coulomb field（PCF） scattering exhibits a significant impact on RSat the above-mentioned different temperatures. Furthermore, in the AlGaN/AlN/GaN HFETs, the interaction between the additional positive polarization charges underneath the gate contact and the additional negative polarization charges near the source Ohmic contact, which is related to the PCF scattering, is verified during the variable-temperature study of RS.
基金Project supported by the National Natural Science Foundation of China (Grant Nos.61306113,60876009,and 11174182)
文摘Ni/Au Schottky contacts on AlN/GaN and AlGaN/GaN heterostructures are fabricated. Based on the measured current-voltage and capacitance-voltage curves, the polarization sheet charge density and relative permittivity are analyzed and calculated by self-consistently solving Schrodinger＇s and Poisson＇s equations. It is found that the values of relative permittivity and polarization sheet charge density of AlN/GaN diode are both much smaller than the ones of AlGaN/GaN diode, and also much lower than the theoretical values. Moreover, by fitting the measured forward 1-V curves, the extracted dislocations existing in the barrier layer of the AlN/GaN diode are found to be much more than those of the AlGaN/GaN diode. As a result, the conclusion can be made that compared with AlGaN/GaN diode the Schottky metal has an enhanced influence on the strain of the extremely thinner AlN barrier layer, which is attributed to the more dislocations.
基金Project supported by the National Natural Science Foundation of China (Grant Nos.60890192,60876009,and 11174182)
文摘Ni/Au Schottky contacts on A1N/GaN and A1GaN/GaN heterostructures are fabricated. Based on the measured current-voltage and capacitance-voltage curves, the electrical characteristics of AlN/GaN Schottky diode, such as Schottky barrier height, turn-on voltage, reverse breakdown voltage, ideal factor, and the current-transport mechanism, are analyzed and then compared with those of an A1GaN/GaN diode by self-consistently solving Schrodinger＇s and Poisson＇s equations. It is found that the dislocation-governed tunneling is dominant for both AlN/GaN and AlGaN/GaN Schottky diodes. However, more dislocation defects and a thinner barrier layer for AlN/GaN heterostrncture results in a larger tunneling probability, and causes a larger leakage current and lower reverse breakdown voltage, even though the Schottky barrier height of AlN/GaN Schottky diode is calculated to be higher that of an A1GaN/GaN diode.
基金Project supported by the Young Scientists Fund of the National Natural Science Foundation of China(Grant No.61401373)the Fundamental Research Funds for Central Universities,China(Grant No.XDJK2013B004)the Research Fund for the Doctoral Program of Southwest University,China(Grant No.SWU111030)
文摘High-performance Al Ga N/Ga N high electron mobility transistors（HEMTs） grown on silicon substrates by metal–organic chemical-vapor deposition（MOCVD） with a selective non-planar n-type Ga N source/drain（S/D） regrowth are reported. A device exhibited a non-alloyed Ohmic contact resistance of 0.209 Ω·mm and a comprehensive transconductance（gm） of 247 m S/mm. The current gain cutoff frequency f T and maximum oscillation frequency f MAX of 100-nm HEMT with S/D regrowth were measured to be 65 GHz and 69 GHz. Compared with those of the standard Ga N HEMT on silicon substrate, the fTand fMAXis 50% and 52% higher, respectively.
