A GaN/Si nanoheterostructure is prepared by growing wurtzite GaN on a silicon nanoporous pillar array （Si-NPA） with a chemical vapor deposition method. The temperature evolution of the photoluminescence （PL） of Ga...A GaN/Si nanoheterostructure is prepared by growing wurtzite GaN on a silicon nanoporous pillar array （Si-NPA） with a chemical vapor deposition method. The temperature evolution of the photoluminescence （PL） of GaN/Si- NPA is measured and the PL mechanism is analyzed. It is found that the PL spectrum is basically composed of two narrow ultraviolet peaks and a broad blue peak, corresponding to the near band-edge emission of GaN and its phonon replicas, and the emission from Si-NPA. No GaN defect-related PL is observed in the as-prepared GaN/Si-NPA. Our experiments prove that Si-NPA might be an ideal substrate for preparing high-quality Si-based GaN nanomaterials or nanodeviees.展开更多
A GaN/Si nanoheterojunction is prepared through growing Ga N nanocrystallites（nc-GaN） on a silicon nanoporous pillar array（Si-NPA） by a chemical vapor deposition（CVD） technique at a relatively low temperature. T...A GaN/Si nanoheterojunction is prepared through growing Ga N nanocrystallites（nc-GaN） on a silicon nanoporous pillar array（Si-NPA） by a chemical vapor deposition（CVD） technique at a relatively low temperature. The average size of nc-Ga N is determined to be ~10 nm. The spectral measurements disclose that the photoluminescence（PL） from GaN/SiNPA is composed of an ultraviolet（UV） band and a broad band spanned from UV to red region, with the feature that the latter band is similar to that of electroluminescence（EL）. The electron transition from the energy levels of conduction band and, or, shallow donors to that of deep acceptors of Ga N is indicated to be responsible for both the broad-band PL and the EL luminescence. A study of the I-V characteristic shows that at a low forward bias, the current across the heterojunction is contact-limited while at a high forward bias it is bulk-limited, which follows the thermionic emission model and space-charge-limited current（SCLC） model, respectively. The bandgap offset analysis indicates that the carrier transport is dominated by electron injection from n-GaN into the p-Si-NPA, and the EL starts to appear only when holes begin to be injected from Si-NPA into GaN with biases higher than a threshold voltage.展开更多
The surface morphology of GaN grown by MOCVD on GaN/Si template was studied.Rough morphology and deep pinhole defects on some surface areas of the samples were observed and studied.The formation of rough morphology is...The surface morphology of GaN grown by MOCVD on GaN/Si template was studied.Rough morphology and deep pinhole defects on some surface areas of the samples were observed and studied.The formation of rough morphology is possibly related to Ga-Si alloy produced due to poor thermal stability of template at high temperature.The deep pinhole defects generated are deep down to the surface of MBE-grown GaN/Si template.The stress originated from the large thermal expansion coefficient difference between GaN and Si may be related to the formation of the pinhole defects.The surface morphology of the GaN can be improved by optimizing the GaN/Si template and decreasing the growth temperature.展开更多
GaN film grown on Si substrate was characterized by Rutherford backscattering/Channeling (RBS/C). The experimental results show that the thick- ness of GaN epilayer is about 2.5 μm and the GaN film has a good crystal...GaN film grown on Si substrate was characterized by Rutherford backscattering/Channeling (RBS/C). The experimental results show that the thick- ness of GaN epilayer is about 2.5 μm and the GaN film has a good crystalline quality (Xmin=3.3%). By using channeling angular scanning. the 0.35% of average tetragonal distortion in GaN layer is observed. In addition, the depth profiles of strain in GaN film layer reveal that the strain in GaN film nonlinearly decreases with the increase of film thickness. The strain-free thickness (above 2.5 μm) of GaN film on Si substrate is far below that (150μm) of GaN film on Sapphire.展开更多
Direct growth of GaN films on Si(001) substrate at low temperatures (620～720℃) by electron cyclotron resonance (ECR) microwave plasma enhanced metalorganic chemical vapor deposition (PEMOCVD).The crystalline phase s...Direct growth of GaN films on Si(001) substrate at low temperatures (620～720℃) by electron cyclotron resonance (ECR) microwave plasma enhanced metalorganic chemical vapor deposition (PEMOCVD).The crystalline phase structures of the films are investigated.The results of high resolution transmission electron microscopy (HRTEM) and X ray diffraction (XRD) indicate that high c axis oriented crystalline wurtzite GaN is grown on Si(001) but there is an amorphous layer formed naturally at GaN/Si interface.Both faces of the amorphous layer are flat and sharp,and the thickness of the layer is 2nm approximately cross the interface.The analysis supports that β GaN phase is not formed owing to the N x Si y amorphous layer induced by the reaction between N and Si during the initial nucleation stage.The results of XRD and atomic force microscopy (AFM) indicate that the conditions of substrate surface cleaned in situ by hydrogen plasma,GaN initial nucleation and subsequent growth are very important for the crystalline quality of GaN films.展开更多
文摘A GaN/Si nanoheterostructure is prepared by growing wurtzite GaN on a silicon nanoporous pillar array （Si-NPA） with a chemical vapor deposition method. The temperature evolution of the photoluminescence （PL） of GaN/Si- NPA is measured and the PL mechanism is analyzed. It is found that the PL spectrum is basically composed of two narrow ultraviolet peaks and a broad blue peak, corresponding to the near band-edge emission of GaN and its phonon replicas, and the emission from Si-NPA. No GaN defect-related PL is observed in the as-prepared GaN/Si-NPA. Our experiments prove that Si-NPA might be an ideal substrate for preparing high-quality Si-based GaN nanomaterials or nanodeviees.
基金Project supported by the National Natural Science Foundation of China(Grant No.61176044)
文摘A GaN/Si nanoheterojunction is prepared through growing Ga N nanocrystallites（nc-GaN） on a silicon nanoporous pillar array（Si-NPA） by a chemical vapor deposition（CVD） technique at a relatively low temperature. The average size of nc-Ga N is determined to be ~10 nm. The spectral measurements disclose that the photoluminescence（PL） from GaN/SiNPA is composed of an ultraviolet（UV） band and a broad band spanned from UV to red region, with the feature that the latter band is similar to that of electroluminescence（EL）. The electron transition from the energy levels of conduction band and, or, shallow donors to that of deep acceptors of Ga N is indicated to be responsible for both the broad-band PL and the EL luminescence. A study of the I-V characteristic shows that at a low forward bias, the current across the heterojunction is contact-limited while at a high forward bias it is bulk-limited, which follows the thermionic emission model and space-charge-limited current（SCLC） model, respectively. The bandgap offset analysis indicates that the carrier transport is dominated by electron injection from n-GaN into the p-Si-NPA, and the EL starts to appear only when holes begin to be injected from Si-NPA into GaN with biases higher than a threshold voltage.
基金Project supported by Special Funds for Major State Basic Research Project(G2000683 and 2002CB311903)Nationel Natural Foundation of China(60136020)Key Imnovation Program of Chinese Academy of Science and National High Technology R&D Pogram of China(2002AA305304)
文摘The surface morphology of GaN grown by MOCVD on GaN/Si template was studied.Rough morphology and deep pinhole defects on some surface areas of the samples were observed and studied.The formation of rough morphology is possibly related to Ga-Si alloy produced due to poor thermal stability of template at high temperature.The deep pinhole defects generated are deep down to the surface of MBE-grown GaN/Si template.The stress originated from the large thermal expansion coefficient difference between GaN and Si may be related to the formation of the pinhole defects.The surface morphology of the GaN can be improved by optimizing the GaN/Si template and decreasing the growth temperature.
基金Supported by National Natural Science Foundation of China under grant(10075072)
文摘GaN film grown on Si substrate was characterized by Rutherford backscattering/Channeling (RBS/C). The experimental results show that the thick- ness of GaN epilayer is about 2.5 μm and the GaN film has a good crystalline quality (Xmin=3.3%). By using channeling angular scanning. the 0.35% of average tetragonal distortion in GaN layer is observed. In addition, the depth profiles of strain in GaN film layer reveal that the strain in GaN film nonlinearly decreases with the increase of film thickness. The strain-free thickness (above 2.5 μm) of GaN film on Si substrate is far below that (150μm) of GaN film on Sapphire.
文摘Direct growth of GaN films on Si(001) substrate at low temperatures (620～720℃) by electron cyclotron resonance (ECR) microwave plasma enhanced metalorganic chemical vapor deposition (PEMOCVD).The crystalline phase structures of the films are investigated.The results of high resolution transmission electron microscopy (HRTEM) and X ray diffraction (XRD) indicate that high c axis oriented crystalline wurtzite GaN is grown on Si(001) but there is an amorphous layer formed naturally at GaN/Si interface.Both faces of the amorphous layer are flat and sharp,and the thickness of the layer is 2nm approximately cross the interface.The analysis supports that β GaN phase is not formed owing to the N x Si y amorphous layer induced by the reaction between N and Si during the initial nucleation stage.The results of XRD and atomic force microscopy (AFM) indicate that the conditions of substrate surface cleaned in situ by hydrogen plasma,GaN initial nucleation and subsequent growth are very important for the crystalline quality of GaN films.
