單軸應力下P型鍺之電性與兆赫波吸收頻譜之研究

Abstract

在本論文我們藉由觀察低溫中應力下鍺摻雜鎵的吸收頻譜，了解雜質能階與價帶頂端(輕電洞帶與重電洞帶)隨應力分裂的情形。我們發現在外加[100] ([110])方向的應力的情況下當應力小於0.5 kBar(1KBar)時雜質基態與激發態間的能階差會隨應力加而上升，而當應力超過0.5KBar(1KBar)時則其隨著應力增加而下降。此外，我們也對樣品施加平行於應力方向之電場，觀察不同應力下電流電壓特性。我們發現崩潰電壓會隨著應力增加也有先上升後下降的趨勢。因此，我們推論載子受激由基態躍遷到激發態的機率，與不同應力下雜質基態與激態間的能階差有關，會影響自由載子於價帶的數量，而造成崩潰電壓隨應力大小改變。

In this study, we measured the I-V and absorption characteristics of strained Ge:Ga samples at cryogenic temperature (10 K). As the stress increases along the [100] and [110] direction, the breakdown voltage increases to a maximum around 0.5-1 kBar and then decreases. The absorption spectra show that the energy differences between the ground states and the excited states also increase to a maximum then decrease in the same stress region. According to these results, we can propose a mechanism to explain the stress dependence of breakdown voltage. Our experiment is in agreement with the theoretical predictions.