Influence of semiconductor surface condition on electrical and photoelectric properties of Al-Zn3P2 contacts

摘要

Zinc phosphide Zn$-3$/P$-2$/ has been intensively investigated as one of the most promising materials for applications in low-cost solar energy converters and broad- range photodetectors. The Schottky barriers formed by Al on Zn$-3$/P$-2$/ p-type crystals have been studied. Substantial differences were observed depending on whether the semiconductor surface was chemically etched, mechanically polished or/and heat treated at 523 K. Measurements of current-voltage characteristics and photovoltaic spectrum of Al-Zn$-3$/P$-2$/ contacts at room temperature have been used for determination of some electrical parameters of junctions as well as optical transitions and hole concentration in the semiconductor. The value of barrier height, $Phi$-B$/, changed from 0.76 to 0.78 eV, the junction depth - from about 3 to 79 $mu@m, and the contact resistance - from 5.9 $MUL 10$+3$/ to 858 $MUL 10$+3$/ approximately ega@. The hole concentration of examined polycrystalline samples was equal to 2 $MUL 10$+13$/ $DIV 5 $MUL 10$+15$/ cm. The condition of semiconductor surface seems to have an essential influence on obtained electrical parameters of Al-Zn$-3$/P$-2$/ junctions and their spectral characteristics. To understand the problems connected with metal-Zn$-3$/P$-2$/ interface layer formation, the free enthalpy, $Delta@G$-R$/, was calculated. The analysis of the results, obtained especially for the Mg and Al, have indicated that Al is also a good candidate for formation of rectifying contacts to Zn$-3$/P$- 2$/.