以液相磊晶法成長砷化鎵磊晶層之特性研究

Characterizations of GaAs epilayer grown by LPE

陳清澤(Ching-Tse Chen)

指導教授 ： 廖森茂

中原大學/工學院/電子工程研究所/碩士(2003年)

https://doi.org/10.6840/cycu200300318

摘要

在本研究中，將詳細說明液相磊晶系統及實驗過程。另外，亦在成功在晶向(100)，半絕緣砷化鎵基板上成長高品質的p型、n型以及超微量摻雜稀土元素鈥之砷化鎵磊晶層。並且針對不同條件下摻雜鍺、碲和鈥，逐一探討成長砷化鎵磊晶層相關之表面型態、結晶、光與電特性。
　　根據實驗結果顯示，隨著碲、鍺摻雜量的增加，能觀察到愈亦粗糙的表面型態。除此之外，當摻雜超過0.0375重量百分比的鈥時，可觀察到磊晶層粗糙的表面型態。
　　在溫度14 K下，透過觀測光激螢光光譜分析，可以得知隨著鍺在砷化鎵磊晶層中摻雜量的增加，其光譜尖峰往低能階位移的趨勢；此外，隨著碲摻雜量的增加，其光譜尖峰則往高能階位移的趨勢。而超微量摻雜稀土元素鈥的濃度在0.0375重量百分比時，與其它摻雜量之磊晶層相較，其光激螢光光譜顯示其最窄之帶緣放射之半波高寬為11毫電子伏特；換言之，在磊晶層成長時，稀土元素對背景雜質之載子吸附效應得以證明。
　　根據在室溫下霍爾量測的結果顯示，隨著鍺或碲摻雜濃度的增加，載子濃度有增加、而載子移動率有減少的趨勢。而此高品質p型與n型之砷之鎵磊晶層，其載子濃度分別高達3.89×1019 cm-3與1.38×1019 cm-3。同時在鈥的摻雜濃度為0.0375重量百分比時，載子濃度可減少至8.76×1015 cm-3，載子移動率則可達到324.14cm2/V-sec。然而，當鈥的摻雜超過此量，則會導致載子濃度的上升與載子移動率的下降，此現象可能是因為鈥的過度摻雜，在磊晶成長中使其扮演施體的角色。
　　透過本研究顯示，以液相磊晶系統成長之砷化鎵磊晶層，有助於改善光電元件之光、電特性。

關鍵字

稀土元素 ； 液相磊晶 ； 砷化鎵

並列摘要

In this thesis, details of the Liquid-Phase Epitaxy (LPE) and the experimental procedures were mentioned here. The high quality p-type, n-type, and slightly rare-earth element Ho-treated GaAs epitaxial layers on semi-insulating (100) oriented GaAs substrate by LPE have investigated.
On surface morphology, Crystallization, optical and electrical properties, effect of Ge, Te, and Ho doped GaAs epilayers have been examined. In these cases of different doping conditions, the growth results are correspondingly distinct.
With the increase of Te- or Ge-doped amount, fairly rough surface morphology could be found. In addition, the Ho weight percentage exceeds 0.0375wt% would gives rise to an inhomogeneous and rough epitaxial surface. The DCXD spectrum of slightly Ho-doped GaAs epilayer with 0.0375 wt% has the narrowest FWHM and the highest intensity.
In the 14K PL spectra of GaAs epitaxial layers, the PL band shifts to lower energy with increasing the Ge doped mole fraction in the p-type layers. Besides, for increasing Te-doping amounts in GaAs the near-band-edge PL spectra are widened while the maximum of the dominant emission is shifted monotonically towards higher energy. The minimum FWHM of slightly Ho-treated samples is 11.03 meV with adding amount of 0.0375wt%, i.e. the gettering effect of rare-elements Ho on the residual impurities during GaAs epilayer growth is confirmed.
Depend on Hall measurement at room temperature, it was found that the carrier concentration increased and the mobility decreased as the Ge or Te mole fraction increased. The high quality p-type and n-type GaAs epilayers with carrier concentration was up to 3.89×1020 and 1.38×1019 cm-3, respectively.
The carrier concentration was reduced to 8.76×1015 cm-3 and mobility was 324.14 cm2/V-sec with Ho doped amount of 0.0375 wt%. An excess of Ho-doping amount, however, leads to the increasing of carrier concentration and the reducing of mobility because the Ho species maybe play a role of donor in the epilayers.
Using LPE growth, the GaAs epilayers investigated in this thesis could be used to fabricate device for better electrical and optical characteristics.

並列關鍵字

LPE ； Rare-earth element ； GaAs

參考文獻

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