Characterizations of GaAs epilayer grown by LPE

• Main Authors: Ching-Tse Chen, 陳清澤
• Other Authors: Sen-Mao Liao
• Format: Others
• Language: en_US
• Published: 2003
• Online Access: http://ndltd.ncl.edu.tw/handle/ru5mte

碩士 === 中原大學 === 電子工程研究所 === 91 === 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.