Polarization effects in 2-DEG and basic solid state physics 2-DHG AlGaN/AlN/GaN multi-heterostructures measured by electron holography

The electrostatic potential profiles and charge distributions in modulation-doped n-type and p-type AlGaN/AlN/GaN hetero-structures have been measured by electron holography with high spatial resolution. For n-type two-dimensional electron gas structure a negative curvature and for p-type two-dimensional hole gas structure a positive curvature in the potential profile at the AlN/GaN interface were observed, which demonstrated the accumulation of two-dimensional carriers. The measured electrostatic potential profiles were also compared with the calculated band diagram in the heterostructures.