摘要
利用高压光致发光方法在液氮温度下和０—３５ｋａｒ的压力范围内对不同层厚的ＧａＡｓ／Ａｌ０．３３Ｇａ０．６７Ａｓ短周期超晶格以及具有相近组份的Ａｌ０．３Ｇａ０．７Ａｓ体材料进行了系统的研究．测得Ａｌ０．３Ｇａ０．７Ａｓ体材料的Γ谷和Ｘ谷的压力系数分别为８．６ｍｅＶ／ｋｂａｒ和－．５７ｍｅＶ／ｋｂａｒ．在一定的压力范围内同时观测到了短周期超晶格中与类Γ态和类Ｘ态相关的发光峰，从而得到了类Γ态能级和类Ｘ态能级随压力的变化关系．首次获得了有关ＧａＡｓ／Ａｌ０．３３Ｇａ０．６７Ａｓ短周期超晶格能带不连续性（包括价带不连续性△Ｅｖ和导带不连续性△Ｅｃ）随压力变化的全部信息．实验结果表明这类短周期超晶格的△Ｅｖ和△Ｅｃ及其压力系数不仅与压力有关，而且与超晶格的周期有关．ｄ△Ｅｖ／ｄＰ和ｄ△Ｅｃ／ｄＰ随着周期的变短分别从（１０，１０）的０．２７ｍｅＶ／ｋｂａｒ和－２．４０ｍｅＶ／ｋｂａｒ增加和减小到（５，４）的４．０ｍｅｙ／ｋｂａｒ和－６．１ｍｅＶ／ｋｂａｒ．这种变化规律主要是由于超晶格中重空穴和Ｘ谷中电子束缚能△ｈｈ和△ｘ的压力系数ｄ△ｈｈ／ｄＰ和ｄ△ｘ／ｄＰ随着超晶格周期变短而迅速增加造成的．
Abstract The photoluminescence (PL) of GaAs/Al0.33Ga0.67As short period superlattices (SPSL's) and bulk Al0.3Ga0.7As have been investigated at 77K under pressure in the range of 0-35kbar. The measured pressure coefficients of the r-valley and X-valley for bulk Al0.3Ga0.7As are 8.6 and - l.57meV /kbar, respectively. The EΓand EX PL peaks attributing to the r-and X-like states to heavy hole transitions in GaAs/Al0.33Ga0.67 As SPSL's were observed in a certain pressure range. The experimental results show that the valence and conduction-band offsets in GaAs/Al0.33 Ga0.67As SPSL's, △Ev and △Ec, depend on pressure and their pressure coefficients,d△Ev/dP and d△Ec/dP, are also related to the period lengths. d△Ev/dP and d△Ec/dp increase and decrease with decreasing period lengths, changing from 0.27 and -2.40meV/kbar for (10, 10) to 4.0 and - 6.1meV/kbar for (5,4), respectively. These are attributed to the increasing of the pressure coefficients of the confinement energies for a heavy hole and an electron in the X valley with decreasing the period lengths.
