Effective Masses for 1 and 2% N in InGaAsN Alloys

It is well known, small amounts of nitrogen to GaAs dramatically decreases the band gap energy. Besides the effect the isoelectronic nitrogen has upon the band gap energy, information regarding the presence of nitrogen on the masses is also important. Here we present conduction-band effective mass determinations for nitrogen concentrations of 1 and 2%. The masses were determined by: (1) Low temperature band gap energy dependence as a function of InGaAsN/GaAs quantum-well width. (2) Room temperature photoreflectance measurements of the ground and excited state energies for InGaAsN/GaAs quantum wells. (3) Low temperature magnetoluminescence measurements of the exciton diamagnetic shift in bulk InGaAsN epilayers. The effective masses are found to be approximately 2 to 3 times heavier than the GaAs value of 0.067. Additionally, the mass pressure coefficients for the effective masses were determined between ambient and 100 kbars from the 2-K magnetoluminescence data. The exciton effective masses are found to very pressure dependent, approaching values of 0.4 at 100 kbar. Theoretical interpretations of the strong pressure dependence will be provided using the results of a first-principles band structure calculation for the InGaAsN alloy system. Finally, a new and novel approach for studying pressure dependent masses based upon the interpretation of excitonic linewidths due to alloy fluctuation theory will be presented.