Nitride-based emitters on SiC substrates

Single crystal thin films with compositions from the AlN-InN-GaN system were grown via metal-organic chemical vapor deposition (MOCVD) on single crystal 6H-SiC substrates. AlGaN containing high and low fractions of Al was grown directly on the SiC for use as a buffer layer. Subsequent epitaxial layers of GaN and AlGaN were doped with Mg and Si to achieve p-type and n-type conductivity, respectively. N-type InGaN layers with In compositions up to similar to 50% were also achieved. Room temperature photoluminescence on these films exhibited single peaks in the spectral range from the UV to green. Various layers were combined to form light emitting diode (LED) and laser structures. Blue LEDs with both insulating and conductive buffer layers exhibited an external quantum efficiency of 2-3% with a forward operating voltage of 3.4-3.7 V. Laser diode structures having a separate confinement heterostructure (SCH) multiple quantum well (MQW) configuration were optically and electrically pumped. Photopumping resulted in stimulated emission at 391 nm. Electrically pumped structures resulted in a peak emission at 393 nm and a bandwidth of 12 nm. No lasing was observed.