Comparative study of (0001) and (11\bar{2}2) InGaN based light emitting diodes

We have systematically investigated the doping of with Si and Mg by metal–organic vapour phase epitaxy for light emitting diodes (LEDs). By Si doping of GaN we reached electron concentrations close to 1020 cm−3, but the topography degrades above mid 1019 cm−3. By Mg doping we reached hole concentrations close to 5 × 1017 cm−3, using Mg partial pressures about 3× higher than those for (0001). Exceeding the maximum Mg partial pressure led to a quick degradation of the sample. Low resistivities as well as high hole concentrations required a growth temperature of 900 °C or higher. At optimised conditions the electrical properties as well as the photoluminescence of p-GaN were similar to (0001) p-GaN. The best ohmic p-contacts were achieved by NiAg metallisation. A single quantum well LED emitting at 465 nm was realised on (0001) and . Droop (sub-linear increase of the light output power) occurred at much higher current densities on . However, the light output of the (0001) LED was higher than that of until deep in the droop regime. Our LEDs as well as those in the literature indicate a reduction in efficiency from (0001) over semi-polar to non-polar orientations. We propose that reduced fields open a loss channel for carriers.