Light-emitting diodes with integrated omnidirectionally reflective contacts

摘要

An electrically conductive omnidirectional reflector (ODR) is demonstrated as p-type ohmic contact for an AlGaInP light-emitting diode (LED). The ODR comprises the semiconductor, a Ag metal layer and an intermediate SiO_2 low-refractive index dielectric layer. The SiO_2 layer, located between the LED semiconductor and the silver layer, is perforated by an array of AuZn micro-contacts thus enabling electrical conductivity. It is shown that the ODR-LED has a significantly higher light-extraction efficiency as compared to LEDs employing distributed Bragg reflectors (DBRs). For devices emitting in the red wavelength range, external quantum efficiencies of 18 % and 11 % are obtained for ODR-and DBR-LEDs, respectively. The performance of the ODR-LED can be further increased by replacing the SiO_2 dielectric with materials having a refractive index 1.45. Performance characteristics of such powerful reflectors will be presented.