MOCVD Growth And Investigation Of Device Performance Of In_0.82Ga_0.18As Infrared Detection Materials

In_xGa_1-xAs material is very important for detectors of near infrared region about 1³μm. Compared with conventional HgCdTe or antimonide materials, the ternary InGaAs material has high electron mobility, good stability, good anti-radiation characteristic, mature growth and device processing technology, and better performance of the photodetectors or arrays, especially at higher operation temperatures and in higher irradiation environment. Its band gap can be varied between 0.35¹.43 eV and has been applied in space remote sensing and infrared imaging fields. In recent years, there are growing needs for high In content InGaAs detectors mainly in applications of aerospace imaging （such as earth observation, remote sensing and environmental monitoring, etc.） and spectroscopy, especially the needs of In_0.82Ga_0.18As detectors with the cut-off wavelength of 2.5μm （corresponding In content about 0.82）. Because of the large lattice mismatch of about 2% existing between the high In content In_0.82Ga_0.18As epilayer and InP substrate, the number of dislocations and defects increases which will degrade the performance of the In_0.82Ga_0.18As detectors. So, it is very important to obtain the high quality In_0.82Ga_0.18As materials. The two-step growth method is one of the most important techniques to solve the growth of materials with large lattice mismatch, in which low temperature growth of buffer layer is followed by the growth of epilayer at higher temperature. Two-step growth method can effectively suppress the dislocations and defects extending to the epilayers, and then improve the crystalline quality of epilayers. In order to obtain high quality In_0.82Ga_0.18As detection materials, In_0.82Ga_0.18As buffer layer was thermal annealed based on the two-step growth method to further improve the crystalline quality of In_0.82Ga_0.18As epilayer. In this paper, In_0.82Ga_0.18As epilayers and the detectors related materials were prepared by optimizing the two-step grow method, and the growth conditions on the crystalline quality of epilayers were investigated, and the performances of the devices based on the In_0.82Ga_0.18As detection materials were also studied. Major contents of study in this paper were listed as follows:1. Growth and characterization study of high quality In_0.82Ga_0.18As materials: In order to improve the crystalline quality of epilayers, annealing treatment was performed on the In_0.82Ga_0.18As buffer layers grown at low temperarures based on two-step growth method. The effect of buffer layer annealing temperature and annealing time on the properties of epilayers was investigated. Based on the experimental results, the crystalline quality and properties were optimum when the buffer layer was thermal annealed at 530 oC for 5 min. In addition, variable temperarure Hall measurements and analysis indirectly indicate that the buffer layer annealing treatment can greatly improve the crystalline quality of epilayers.2. Growth and characterization study of InAs_0.6P（0.4） used as window materials of In_0.82Ga_0.18As detectors: Two different materials InAs_0.6P（0.4） and In_0.82Ga_0.18As were used as low-temperature buffer layers to prepare InAs_0.6P（0.4） epilayers on InP substrates.The effect of growth conditions of buffer layers and epilayers on the crystalline quality of InAs_0.6P（0.4） materials was studied. The results show that, the crystalline quality of InAs_0.6P（0.4） epilayer using In_0.82Ga_0.18As as buffer layer was better than that using InAs_0.6P（0.4） as buffer layer. When In_0.82Ga_0.18As was used as buffer layer, the optimum epilayer’s growth temperature was around 580 oC and the buffer layer thickness was 100 nm. This provides a reference for growth of InAs_0.6P（0.4） material used as window layer for In_0.82Ga_0.18As infrared detectors.3. The study of In_0.82Ga_0.18As structure materials and performance of In_0.82Ga_0.18As infrared detectors: The thickness of absorption and cap layer of the device structure was optimized. The large area InP/In_0.82Ga_0.18As/InP material and InAs_0.6P（0.4）/In_0.82Ga_0.18As/InP material were grown. The planar type of PIN single element, 4×2 element linear arrays and 256×1 element linear arrays were fabricated, and the performance of devices was discussed.