Investigation of Chemical Wet-Etch Surface Modification of Ga0.5In0.5P Using Photoluminescence X-Ray Photoelectron Spectroscopy, Capacitance Measurements, and Photocurrent-Voltage Curves

Epitaxial Ga_0.5In_0.5P films, deposited lattice-matched to GaAs by atmospheric pressure organometallic vapor phase epitaxy, were subjected to various wet-etching processes and the resulting surface was characterized. The steady state photoluminescence (PL) peak intensity was found to increase 5-fold with some etches, indicating lowered surface recombination rates as a result of etching. Average PL decay times estimated from time-resolved photoluminescence studies also exhibited a correspondingly significant enhancement. Capacitance-voltage and photocurrent-voltage measurements were carried out to investigate changes in energetics of the band edges or alteration in kinetics as a result of the treatments. High resolution X-ray photoelectron spectroscopy revealed a variation of the oxidized species of P, Ga, and In on the surface with etching and were correlated to the PL results. The amount of oxidized material on the surface was lowered after etching in concentrate H₂SO₄, 1:20:1 HCl:CH₃COOH:H₂O₂, and 1:20:1 HCl:H₃PO₄:H₂O₂ and lowered with observations of a higher steady-state PL intensity and longer carrier lifetimes. A nitric acid or aqua regia etch on the other hand yielded an oxide-rich surface with diminished PL.