Study Of The Effects Annealing On The Native Defects And Electrical Properties In Ndsilec GaAs

GaAs crystal is an excellent III-V compound semiconductor material and is widely used as the material for the fabrication of microwave device and photo-electrical device and ultra high speed integrated circuit. NDLECSI GaAs crystal means to the nonintentionally doped (ND) semi-insulating (SI) liquid encapsulated czochralski (LEG) GaAs crystal. Native defect EL2 is the dominant donor defect in NDLECSI GaAs, it plays a crucial role in electrical compensation of GaAs materials. As-grown NDLECSI GaAs often manifests the distribution inhomogeneity of the EL2 and thermal instability of electrical parameters. These have great effects on the performance of the device based on GaAs. The annealing may improve the homogeneity of EL2, but the electrical parameters of GaAs often take place considerably change after the annealing procedure. The mechanism for annealing to affect both the distribution and the electrical parameters is not fully understood. So, it has important significance to study the effects of annealing on the native defect EL2 and electrical parameters of NDLECSI GaAs crystal.This paper has studied respectively the mechanism for the annealing affects native defect EL2 and electrical parameters of NDLECSI GaAs crystal. The annealings are carried out for as-grown NDLECSI GaAs in the different temperature range under different ambient gas and cooling process conditions. The effects of the annealings on EL2 concentration EL2 distribution and electrical parameters of GaAs crystal are systematically studied. Considering the EL2 defect related to excess As, the changes of As precipitate and dislocation caused by the annealing have been also researched by AB chemical etching method. The electrical parameters of GaAs crystal are examined by Hall effect measure system and the EL2 concentration is determined by multiple wavelengh infrared absorption method. The results are as follows-.The EL2 concentration of NDLECSI GaAs takes place the different change after different annealing. The annealing has improvement effect on the EL2 distribution inhomogeneity.According to the experimental results, it is presented that the interactive transformation among the three forms of excess As (EL2 , As precipitate and As native point defect) is the dominant cause for EL2 concentration to vary. The improvement of the annealing on the EL2 homogeneity is because the interactive transformation of three excess As forms during annealing resulted to the redistribution of EL2 inNDLECSI GaAs crystal.The electrical parameters of NDLECSI GaAs produce the different change after different temperature annealings, including the transformation of surface conductance ^ the changes of bulk electrical parameters and the transformation of bulk conductance. Increasing the As pressure during annealing can suppress the change of the electrical parameters. It is presented that the causes for the transformation of surface conductance are the generation of GaAs acceptor defect caused due to As vaporization in sample surface and the decreasing of EL2 concentration caused by the out-diffusion of EL2. The presence of As pressure suppress the generation of GaAs and the out-diffusion of EL2, so suppress the transformation of surface conductance in sample. The changes of bulk electrical parameters are because the out-diffusion of As interstitial causes the generation of acceptor defects, VGa, GaAs and Ga^ VGa under the conditions of high temperature and low As pressure. Increasing the As pressure during annealing may suppress the generation of acceptor defects, so may inhibit the changes of bulk electrical parameters. The transformation of bulk conductance is due to the greatly decreasing of EL2 concentration under the conditions of high temperature quenching. Increasing the As pressure during annealing may accelerate the regeneration of EL2 after high temperature quenching and suppress the transformation of bulk conductance.