Two-subband occupation by 2D electrons in MgZnO/ZnO heterostructures

We demonstrate the population of the second quantized subband by the two-dimensional electron system in a MgxZn1-xO/ZnO heterostructure by means of magnetotransport and magnetooptical studies. The second subband is occupied when x= 0.25 and the total electron density is 4.0 x 10(12) cm(-2). The photoluminescence (PL) spectra permit evaluation of the electron density from the characteristic magneto-oscillations of the PL intensity from the second subband. In addition, the electron concentration in the second subband was estimated from the PL linewidth to be around 5 x 10(11)cm(-2), in good agreement with transport data. The energy of the intersubband splitting is quantified at about 27 meV. (C) 2019 The Japan Society of Applied Physics