Growth and properties of VPE GaP for green LEDs

Abstract

The PH3-HCl-Ga-H2 technique for VPE growth of GaP is described. The influence of various growth parameters, including substrate temperature, orientation, and PH3 flow rate on morphology and growth rate are described. For both VPE and LPE nitrogen doping is known to be a major factor in obtaining high green luminescence efficiency. The major emphasis of this paper is an examination of the effect of nitrogen concentration in the range less than 1019 cm−3 (using the Lightowlers correction factor) on the growth process and materials properties, such as defect structure, photoluminescence spectra (at 300 and 77K) and photoluminescence intensity and lifetime. The LED device performance (B/J and efficiency) is used as the final test of material quality. Nitrogen is found to be incorporated far in excess of the solubility limit, and the solid gas distribution coefficient for nitrogen is found to increase rapidly with decreasing temperature below 840°C . The optimum nitrogen concentration for high diode efficacy, photoluminescence intensity, and lifetime is found to be approximately 5 × 1018 cm−3, where diodes fabricated by Zn diffusion into the VPE GaP have efficiencies at a current density of 10 A/cm2 of 0.1%, comparable to the state-of-the-art in the more widely used grown p-n junctions using LPE.