摘要
随着碲镉汞(HgCdTe)红外探测器的不断发展,碲镉汞波长已经逐渐从中波向长波/甚长波方向发展,表面效应很大程度上决定了碲镉汞红外焦平面探测器的性能,因此对表面钝化提出了更高的要求。文中通过研究磁控溅射生长的钝化层进行三温段退火改善长波器件性能,实验结果表明低温段(120~170℃)退火显著改善膜层的致密性,二次离子质谱(Secondary ion mass spectroscopy)表明高温段(320℃/2.5 h)退火高组分层厚度达到0.22μm,改善器件的表面漏电流;第三段低温(200~270℃)稳定载流子浓度在1.0×10^(16)~3.0×10^(16) cm^(-3)范围内。三温段退火工艺提高了钝化膜层的致密性、增大了碲镉汞界面的高组分过渡层厚度的同时稳定了碲镉汞材料的电学参数,为长波碲镉汞红外器件的发展奠定了基础。
Objective With the continuous development of mercury cadmium telluride(HgCdTe)infrared detectors,the operational wavelength of HgCdTe has progressively shifted from mid-wave to long-wave and very long-wave,imposing higher demands on device performance such as resolution,reliability,and sensitivity.As a narrowbandgap semiconductor device,the surface of HgCdTe infrared focal plane detector chips is susceptible to fixed charges introduced by contamination or dangling bonds,which can cause band bending of one to several bandgap magnitudes.This leads to accumulation,depletion,or inversion at the surface of HgCdTe materials,thereby increasing the surface leakage current and severely degrading device performance.Additionally,the high activity of Hg atoms in the material and the relatively low bond energy of Te-Hg bonds make Hg prone to escape,resulting in a Te-rich surface that further impacts device performance.Therefore,surface passivation is a critical step in the fabrication process of HgCdTe photovoltaic infrared focal plane detectors.Methods N-type Hg1-xCdxTe thin films were grown on cadmium zinc telluride(CdZnTe)substrates using horizontal liquid phase epitaxy.A CdTe/ZnS passivation layer was deposited via magnetron sputtering,and the schematic structure is shown in Fig.1(a).After passivation film growth,the samples were diced using a wafer saw and subjected to interdiffusion annealing under different conditions.The entire annealing process was carried out in a nitrogen atmosphere,with temperature fluctuations kept within 4℃after reaching the set temperature.After annealing,the samples were cooled to room temperature over 25–35 minutes.Subsequently,dry etching was performed to open contact holes,and metal electrodes were deposited to complete the fabrication of long-wave HgCdTe devices,as illustrated in Fig.1(b).Results and Discussions Based on the improved three-stage annealing process described above,it was applied to long-wave mercury cadmium telluride unit devices.Figure 8 presents the corresponding I-V test results.The long-wave devices fabricated using the high-temperature three-stage annealing process exhibit superior performance under reverse bias voltage compared to those prepared by the traditional annealing process,particularly in the region where the reverse bias voltage exceeds 150 mV.This phenomenon is primarily attributed to the high-temperature three-stage annealing process,which enables the formation of higher-quality passivation layer crystal structures and thicker high-composition transition layers.As a result,the fixed charge density and defect state density on the material surface are significantly reduced,ultimately leading to a decrease in the leakage current of the long-wave devices.Conclusions The quality of the surface passivation film grown by magnetron sputtering and the thickness of the high-composition transition layer have a decisive impact on the performance of mercury cadmium telluride(HgCdTe)infrared devices.To address the conflict between the thickness of the high-composition transition layer and the minority carrier lifetime of the material in traditional annealing processes,we innovatively proposed a three-stage annealing process.This process not only successfully prepared high-quality CdTe passivation films and achieved a thicker high-composition transition layer but also significantly improved the minority carrier lifetime of the material,thereby achieving synergistic optimization of passivation film quality,high-composition transition layer thickness,and material minority carrier lifetime.Experimental results show that long-wave infrared devices fabricated using the three-stage annealing process exhibit significantly improved reverse leakage current levels in I-V characteristic tests,especially under high reverse bias voltages,where the leakage current is markedly reduced,leading to enhanced device performance.In the future,we will further optimize the annealing process parameters,explore more refined temperature and time control strategies,and extend the application of this process to long-wave HgCdTe infrared focal plane devices to verify its universality and scalability.
作者
王文
司洋
李轶民
王海澎
杨超伟
刘艳珍
王茹彤
赵贵琴
王向前
宋林伟
李雄军
WANG Wen;SI Yang;LI Yimin;WANG Haipeng;YANG Chaowei;LIU Yanzhen;WANG Rutong;ZHAO Guiqin;WANG Xiangqian;SONG Linwei;LI Xiongjun(Kunming Institute of Physics,Kunming 650223,China)
出处
《红外与激光工程》
北大核心
2025年第7期92-100,共9页
Infrared and Laser Engineering
基金
云南省科技人才与平台计划项目(202105AD160047)。
关键词
碲镉汞
长波
钝化
三温段退火
mercury cadmium telluride
LWIR
passivation
three-stage temperature annealing
