常压MOCVD法生长的p型ZnSe及其光电特性

本文通过常压MOCVD方法,利用NH₃气作为受主掺杂源,在(100)方向的GaAs衬底上生长了ZnSe:N膜。通过测量77K温度下光致发光光谱。观测到了由于掺氮引起的自由到束缚发射(FA)和深中心复合(SA).在低掺杂浓度下FA起主要作用,随着NH₃气浓度增加,FA和SA带的强度随之增强,在重掺杂下SA带成为主要,同时带的半宽度展宽。室温下霍尔测量的结果表明。低掺杂浓度下ZnSe:N膜呈高阻态,而在高掺杂浓度下外延膜呈现P型电导,载流子浓度P～1016cm³.利用p-ZnSe/n-GaAs构成异质pn结,观测到了二极管的整流特性,进一步证实p型ZnSe的实现。

GROWTH AND OPTOELECTRONIC PROPERTIES OF p-TYPE ZnSe BY AP-MOCVD

The nitrogen doped p-type ZnSe on (100) GaAs substrates has been grown by atmospheric pressure (AP) metal organic chemical vapour deposition (MOCVD).Pure NH3 gas was used as a doping material.The nitrogen doping level was controlled by the NH3 gas flow rate.Because sticking coefficients of NH3 molecules appear to be very low,the NH3 flow rate must be great enough to provide sufficient doping of N.This leads to cause degradation of the epilayer quality.Above result is clearly indicated by measurements of X-ray diffraction and photoluminescence(PL).Obtaining of p-type conduction in ZnSe is evidenced by measuring optical and electrical properties of N-doped ZnSe layers.At the low doping level, the PL spectrum exhibited a dominant free-to-acceptor transition (FA) emission at 460um and also exhibited deep centre emission at 580um.ZnSe layers with a low doping level have a very high resistivity.It was difficult to determine theconduction type due to a large Hall-voltage drift.Both band intensities increased with increasing NH3 flow rate.The results indicate that the shallow acceptor and deep centre levels were formed by doping nitrogen.In the high doping level, the 77K PL of the epilayers is dominated by the deep centre emission at 580urn and the bands broadened.The ZnSe layer clearly indicated a p-type conduction by Hall measurements at room temperature.Hall mobilities is nearly 46cm2/V·s and carrier concentrations reach the order of 1016cm3.The p-ZnSe/n-GaAs heterojunctions exhibit good rectification properties.The forward-bias turn-on voltage is 1.5V.The results confirmed the p-typeconduction of the N-doped ZnSe layers with a high doping level.