Published online by Cambridge University Press: 26 February 2011
Low temperature photoluminescence was studied in a large number of pseudomorphic HEMT's having an InxGa1−xAs quantum well. The spectra show strong qualitative differences when the Fermi level is above or below the second conduction subband, and in the latter case they are power dependent. A slight enhancement is seen at the Fermi edge only when it lies close to the higher subband. Excellent agreement is found between the measured Fermi energy and the two-dimensional carrier density in the well.