Comment on 'Piezoelectric effect on Al_(0.35-δ)In_(δ)Ga_(0.65)N/GaN heterostructures' [Appl. Phys. Lett. 80, 2684 (2002)]

摘要

In a recent letter, Lo et al. reported measurements of the longitudinal magnetoresistance R_(xx) of the two-dimensional electron gas (2DEG) in an Al_(0.35-δ)In_(δ)Ga_(0.65)N/GaN heterostructure as a function of magnetic field B normal to the heterointerface. The main observation of that work was two oscillations beat each other, which was interpreted as the population of the lowest two subbands, which yielded that the electric field at the interface was one order of magnitude smaller than that of an Al_(0.35)Ga_(0.65)N/GaN heterostructure. Therefore, they concluded that a small fraction of In atoms in the Al_(0.35-δ)In_(δ)Ga_(0.65)N/GaN could be used as a tuning parameter to control the strain and the piezoelectric field at the interface. In this comment, it is argued that, evidently, the beating oscillations do not directly originate from two-subband Shubnikov-de Haas (SdH) oscillations and a small fraction of In atoms in Al_(0.35-δ)In_(δ)Ga_(0.65)N/GaN cannot affect the piezoelectric field at the interface.