GaAs and InP single crystal growth and their characterisation

摘要

GaAs and InP single crystals are grown using Liquid Encapsulated Czochralski (LEC) technique as ingots, then cut as wafers and polished for the fabrication of devices. The important crystal characteristics such as resistivity, carrier concentration, mobility and the presence of sub-band levels have been studied using various electrical and optical measurements. The structural analysis has been carried out using etching and X-ray topography. For the realisation of metal-semiconductor contacts, Ag, Al and Au Schottky barrier diodes (SBDs) were fabricated and characterised using current-voltage (Ⅰ-Ⅴ), capacitance-voltage (C-V) and deep level transient spectroscopy. A test solar cell has been fabricated on our GaAs crystal and the efficiency of the cell has been determined to be 14.8% as compared to the 17% of the commercial GaAs solar cells. The polished samples are used for liquid phase epitaxial growth. Very good binary and ternary layers are grown on the pBN grown semi-insulating GaAs samples using Liquid Phase Epitaxial technique. High energy and low energy ion implantation studies were carried out using various ions and the results will be presented. Laser Raman studies were carried out on the implanted samples to understand the crystallisation mechanism. Results obtained on the fabrication of p-InP/ITO, p-InP/CdS solar cell device structures will be discussed.