Postfabrication native-oxide improvement of the reliability of visible-spectrum AlGaAs–In(AlGa)P p-n heterostructure diodes

Abstract

Data are presented on the electrical behavior and the reliability of postfabrication native-oxide-passivated visible-spectrum AlGaAs–In(AlGa)P p-n heterostructure light emitting diodes (LEDs). The LEDs are oxidized (H2O+N2, 500 °C, 1 h) after metallization, thus sealing all exposed AlGaAs crystal at cracks, fissures, and edges against atmospheric hydrolysis without degrading their light-output characteristics. The current–voltage (I–V) characteristics of the oxide-passivated LEDs are shown to exhibit normal p-n diode behavior (∼1.9 V at 20 mA). The reliability of the oxidized devices in high-humidity conditions is greatly improved compared to otherwise identical unoxidized LEDs. The latter degrade to less than 50% of initial output power at 1500 h accelerated life test in high-humidity environments, compared to the oxidized LEDs not degrading noticeably in output power after 2500 h.