Soft X-ray ARPES images 2D electron and hole gases in GaN/AlN heterostructures

Soft X-ray ARPES measurements mapped the momentum-space dispersions of two-dimensional electron and hole gases located several nanometers below the surface in undoped GaN/AlN heterostructures. The technique bypassed surface-sensitivity limits of vacuum-ultraviolet ARPES and allowed direct comparison of the observed subband dispersions with transport data.

Chemical gating approach Controlled oxygen adsorption altered the surface potential and produced measurable shifts in the band positions, demonstrating a chemical route to tune the carrier gases. The same method avoids leakage currents that typically hinder electrostatic gating in these wide-bandgap structures.

Research context and support The work was performed at the Swiss Light Source with additional characterization at Cornell University facilities. Funding came from the National Science Foundation, Microsoft Corporation, the Department of Defense Microelectronics Commons Program, and the Army Research Office.