“ Observation of High Carrier Concentrations in Ge - doped GaN : Growth , Characterization & Application

Number of Papers published in peer-reviewed journals: Final Report: Ultraviolet Polariton Laser Report Title Significant progress was achieved in the epitaxy of deep UV AlN/ AlGaN Bragg mirrors and microcavity structures paving the way to the successful fabrication of vertical cavity emitting laser structures and polariton lasers. For the first time DBRs providing sufficient high reflectivity for polariton emission were demonstrated. Thanks to a developed strain balanced Al0.85Ga0.15N template, the critical thickness before cracking could be enhanced to 1.95 μm. The fabricated 25.5 pair AlN/ Al0.65Ga0.35N DBR exhibit a maximum reflectivity above 98% at a Bragg wavelength of 270 nm. In addition a relaxation mechanism by introducing periodic low temperature relaxation layers during DBR growth was proposed a demonstrated. No effect of the LT-AlN layers on the optical properties of the DBR was found. A partially relaxation of the DBR structure by the incorporated interlayers allows to increase the critical layer thickness in order to grow crack-free high reflective DBRs above 99%. The practical implementation of our DBRs and multiple quantum well active regions was demonstrated by the fabrication of a full resonant half microcavity structure. Spectral resonance between the center wavelength of the stop band of the DBR and the MQW emission wavelength was found across the full radius region of the wafer. (a) Papers published in peer-reviewed journals (N/A for none) Enter List of papers submitted or published that acknowledge ARO support from the start of the project to the date of this printing. List the papers, including journal references, in the following categories: (b) Papers published in non-peer-reviewed journals (N/A for none) Received Paper