Due to changes in the spontaneous and piezoelectric polarization, AlGaN/GaN heterostructures exhibit strong polarization fields at heterointerfaces. For quantum wells, the polarization fields lead to a strong band bending and a redshift of the emission wavelength, known as quantum-confined Stark effect. In this paper the polarization fields of thin AlGaN layers in a GaN matrix were determined by evaluating the changes in the depletion region width in comparison to a reference sample without heterostructure using capacitance–voltage-measurements. The polarization fields for Al0.09Ga0.91N (0.6 ± 0.7 MV cm−1), Al0.26Ga0.74N (2.3 ± 0.6 MV cm−1), Al0.34Ga0.66N (3.1 ± 0.6 MV cm−1), Al0.41Ga0.59N (4.0 ± 0.7 MV cm−1) and Al0.47Ga0.53N (5.0 ± 0.8 MV cm−1) heterostructures were determined. The results of the field strength and field direction of all samples are in excellent agreement with values predicted by theory and a capacitance–voltage based Poisson-carrier transport simulation approach giving experimental evidence for a nonlinear increasing polarization field with Al-concentration.
KAUST Repository Item: Exported on 2020-10-01
Acknowledged KAUST grant number(s): BAS/1/1664-01-01, URF/1/3437-01-01, REP/1/3189-01-01
Acknowledgements: This work was supported by the German Federal Ministry of Education and Research (BMBF) within the Advanced UV for Life project and by the Deutsche Forschungsgemeinschaft (DFG) within the Collaborative Research Centre Semiconductor Nanophotonics (SFB 787). Part of this work was also co-funded by the Erasmus+ programme of the European Union. The KAUST authors acknowledge the support of KAUST Baseline BAS/1/1664-01-01, KAUST CRG URF/1/3437-01-01, and GCC REP/1/3189-01-01.