Epi-n-IZO thin films/Æ100æ Si, GaAs and InP by L-MBE––a novel feasibility study for SIS type solar cells

High quality epitaxial indium zinc oxide (heavily indium oxide doped) (epi-n-IZO) thin films were optimized by laser-molecular beam epitaxy (L-MBE) i.e., pulsed laser deposition (PLD) technique for fabricating novel iso- and hetero-semiconductor–insulator–semiconductor (SIS) type solar cells using Johnson Matthey ‘‘specpure’’- grade 90% In2O3 mixed 10% ZnO (as commercial indium tin oxide (ITO) composition) pellets. The effects of substrate temperatures, substrates and heavy indium oxide incorporation on IZO thin film growth, opto-electronic properties with Æ10 0æ silicon (Si), gallium arsenide (GaAs) and indium phosphide (InP) wafers were studied. As well as the feasibility of developing some novel models of iso- and hetero-SIS type solar cells using epi-IZO thin films as transparent conducting oxides (TCOs) and Æ1 00æ oriented Si, GaAs and InP wafers as base substrates was also studied simultaneously. The optimized films were highly oriented, uniform, single crystalline approachment, nano-crystalline, anti-reflective (AR) and epitaxially lattice matched with Æ10 0æ Si, GaAs and InP wafers without any buffer layers. The optical transmission T (max)P95% is broader and absolute rivals that of other TCOs such as ITO. The highest conductivity observed is r ¼ 0:47 103 X 1 cm 1 (n-type), carrier density n ¼ 0:168 1020 cm 3 and mobility l ¼ 123 cm2/V s. From optoelectronic characterizations, the solar cell characteristics and feasibilities of fabricating respective epi-n-TCO/Æ100æ wafer SIS type solar cells were confirmed. Also, the essential parameters of these cells were calculated and tabulated. We hope that these data be helpful either as a scientific or technical basis in semiconductor processing. 2004 Elsevier Ltd. All rights reserved.