表面累积层对N型Hg_(1-x)Cd_xTe输运特性及复合特性的影响

THE INFLUENCE OF SURFACE ACCUMULATION LAYER ON TRANSPORT AND RECOMBINATION PROPERTIES IN N-Hg_(1-x)Cd_xTe

通过测量经紫外辐照的样品的磁输运特性和复合特性,研究N^+表面累积层对钝化N-Hg_(0.78)Cd_(0.22)Te的影响。紫外辐射使N^+表面层减少,从而使样品的电阻增大,这一现象与钝化氧化层俘获电子有关。观察到紫外辐照可使样品的载流子寿命减小约90%。假设紫外辐射降低了由N^+表面层引起的内建电势,可解释较快的电子-空穴复合速率。被激发成准平带或弱耗尽状态的晶体的电子-空穴复合时间常数较小。N-Hg_(1-x)Cd_xTe表面层状态确定了光电导器件的最终设计。

Magnetotransport and recombination have been measured under UV-irradiadtion in order to find out the role of the N^+-surface accumulation layer in passivate N-Hg_(0.78)Cd_(0.22)Te. The reduction of the N^+-surface layer upon UV-irradiation induced an increase in the sample resistance. This is related to trapping of electron in the passivation oxide film. In addition, a tenfold decrease of carrier lifetime is observed after UV-irradiation. This faster electron-hole recombination rate is explained by assuming that the N^+/N built-in potential (due to the N^+ surface layer) is reduced by UV-irradiation. The crystal is driven into 'quasi' flat-band or weak depletion conditions, with a smaller time constant for electron-hole recombination. The appearance of this surface layer determines the ultimate design of semiconductor devices of N-Hg_(1-x)Cd_xTe.