ELECTRON-GAS IN MODULATION-DOPED GAN ALGAN STRUCTURES/

We report low temperature photoluminescence (PL), time resolved PL and electrical transport measurements related to the two-dimensional elec tron gas (2DEG) in GaN/AlGaN heterostructures and quantum wells grown by MOVPE on sapphire. Electrical measurements of the heterostructure s amples show a room temperature mobility of up to 1300 cm(2) V-1 s(-1) and carrier concentration of 10(13) cm(-2). The Pt, spectrum at low te mperatures shows a broad emission about 50 meV below the bulk exciton emission, attributed to recombination involving electrons from the low est subband of the 2DEG at the GaN/AlGaN heterointerface and photoexci ted holes in the GaN layer. The data agrees with a self consistent cal culation of the energy levels and the electron concentration at the in terface. The modulation doped GaN/AlGaN quantum well had an electron c oncentration of 3.0 x 10(12) cm(-3) and a mobility of 850 cm(2) V-1 s( -1) at 300 K. In the low temperature PL spectra we observed three well defined peaks, at 3.53, 3.58 and 3.62 eV, which we attribute to recom bination processes in the quantum well (QW). (C) 1997 Elsevier Science S.A.