Back-Contacted GaInP/GaAs LED Structures by Ex-Situ Dopant Redistribution

Abstract

Compound semiconductor devices utilizing interdigitated back-contact (IBC) designs with a uniform active region (AR) can enable a new generation of optoelectronic devices with eliminated contact shading, reduced resistive losses, and minimal current crowding. However, appropriate lateral doping techniques for such devices are not yet established. This work demonstrates selective-area diffusion doping from an epitaxially grown dopant source layer enabling the fabrication of GaAs-based light-emitting diodes (LEDs) utilizing diffusion-driven charge transport (DDCT) and the IBC design. The effects of doping and device dimensions are analyzed by comparing current-voltage characteristics and electroluminescence (EL) of laterally doped DDCT structures and control structures with several characteristic finger widths between 15 and 300 µm. Additional simulations confirm that the DDCT structure enables effective carrier injection into a buried AR outside the p-n junction. A current density of 1.25 A/cm 2 was measured for the fabricated DDCT-LED with 15-µm wide fingers at a moderate bias voltage of 1.3 V. The light emission from the DDCT-LEDs shows clear signs of lateral current injection, improved current spreading, and a tenfold increase in EL, when compared to control structures specifically designed to validate the presence of diffusion doping. These results indicate that diffusion doping can enable the means to fabricate DDCT structures with effective carrier injection into a uniform AR.