GaN/SiC异质结的慢正电子研究

Study of GaN/SiC contact using slow positron beam

通过对不同生长厚度GaN/SiC(n-n)的慢正电子研究,发现在GaN/SiC的界面中存在大量各种缺陷并在界面两端形成两个不同方向的电场.这些缺陷的产生和SiC衬底表面制备以及GaN和SiC不同的热膨胀系数有关.而缺陷中大量的带状缺陷在界面中形成一个费米能级钉扎(Fermi level pinning),它的存在使界面中存在一定高度的势垒,导致在界面两端的一定区域内形成两个不同方向的电场.用VEPFIT模拟该电场的存在,分四层(GaN/Interface/SiC1/SiC2)进行拟合,得到了很好的拟合效果,并可以给出电场的确定数值.这些电场的存在对正电子的湮没产生了重要影响,使得在SiC区域,有电场的区域内正电子的有效扩散长度减小.界面两端电场大小和界面的带电量以及界面宽度等信息有关,故对该电场的研究可以为研究真实的界面层及其性质的可能应用提供有效的参考价值.

Using a slow positron beam and the program VEPFIT, we found there exists a barrier in the interface between GaN and SiC, which is caused by lots of band-like defects existing in it. The existence of the barrier induced two backing electric fields in diverse directions close to the interface. These fields can produce a longer diffusion length in the SiC region where no field exists compared with that of SiC region, which has an electric field at a set value. The fitted value of the electric field offers a good reference for studying the situation in a real the interface.