Piezoelectric polarization in GaInN/GaN heterostructures and some consequences for device design

The polarization properties of doped Ga0.85In0.15N/GaN multiple quantum wel l structures are investigated under the application of external bias voltag es. From Franz-Keldysh oscillations at and above the barrier band edge, the electric field in the barriers is determined. From the bias dependence, we derive the polarity and an offset of 0.51 MV/cm of the internal field. Thi s is attributed to the piezoelectric polarization in the well region of mag nitude P = -e(z) (0.009 - 0.014) C/m(2). We find that Si doping at typical concentrations of 3 x 10(18) cm(-3) cannot screen the polarization effects on the length scale typical for quantum wells and superlattices but induces large potential barriers.