热处理中As压对半绝缘GaAs缺陷的影响

Effects of As Pressure Duing Annealing on Defects for Semi-insulating GaAs

在 95 0°C和 1 1 2 0°C温度下 ,对非掺杂半绝缘 LECGa As进行了不同 As气压条件下的热处理 ,热处理的时间为 2～ 1 4小时。发现不同 As压条件下的热处理可以改变 Ga As晶片的化学配比 ,并导致本征缺陷和电参数的相应变化。在 95 0°C和低 As气压条件下进行 1 4小时热处理 ,可在样品体内 (表面 1 5 0 μm以下 )引入一种本征受主缺陷 ,使电阻率较热处理前增加约 5 0 % ,霍尔迁移率下降 70 %。这种本征受主缺陷的产生是由于热处理过程中样品内发生了 As间隙原子的外扩散。提高热处理过程中的 As气压可以抑制这种本征受主缺陷的产生。真空条件下在 1 1 2 0°C热处理 2～ 8小时并快速冷却后 ,样品中的主要施主缺陷 EL2浓度约下降一个数量级 ,提高热处理过程中的 As气压可以抑制 EL2浓度下降。这种抑制作用是由于在高温、高 As气压条件下 。

Undoped semi insulating LEC GaAs crystal wafers have been annealed at 950 °C and 1 120 °C under various As gas pressures. The duration of the annealing is 2～14 hrs.It is found that the interior stoichiometry of GaAs crystal wafers can be modified by annealing and the modification in stoichiometry can results in respective changes in intrinsic defects and electrical properties. The bulk resistivity (deeper than 150 μm beneath surface) increases by about 50%, and the Hall mobility decreases by about 70% after an annealing at 950 °C for 14 hrs under low As gas pressure. These changes in the electrical parameters originate from the creationg of an intrinsic acceptor defect species in interior region of the crystal wafers during annealing. The generation of this intrinsic acceptor defect is due to the occurrence of the out diffusion of As interstitials during the high temperature process, which can be suppressed by increasing the As gas pressure during annealing. By evacuated annealing of 2～8 hrs at 1 120 °C followed by fast cooling, the concentration of main native donor defect EL2 in sample can be decreased by nearly one order of magnitude. The decrease in EL2 concentration can also be suppressed by increasing As gas pressure during annealing, and the suppression effect is due to the occurrerce of in diffusion of As interstitials under high temperature and high As gas pressure.