Fabrication of Heterojunction LEDs for Operation at 1.3 Micrometers.

Abstract : This report describes research undertaken to study and optimize the device properties of 1.3-micron InGaAsP edge-emitting LEDs fabricated by both vapor-phase epitaxy (VPE) and liquid-phase epitaxy (LPE). Edge-emitting LEDs have been prepared with both growth methods with a combination of properties rivaling the best reported to date. In the previous final report (RADC-TR-80-110) details of the VPE growth process were presented. Details of the LPE growth process are presented here. The LED efficiency of LPE devices was found to increase with decreasing cavity thickness. A value over 1% was measured with a 1000 lambda. Contact stripe width and coupling technique were also varied to achieve maximum power into an optical fiber. The best coupling was obtained with a 12-micron-wide contact stripe. Significantly better coupling was also achieved with a balled, rather than cleaved, end fiber. More than twice the power could be coupled into a 100-micron core diameter fiber, as compared to a 50-micron core fiber. The temperature dependence of LED emission was also measured for both VPE and LPE devices. LED efficiency dropped over 30% between 20 and 70 C, while an emission wavelength shift of 5 to 6 lambda/C was observed over the same temperature range.