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<p>Gallium nitride (GaN) and aluminum nitride (AlN) host high-density two-dimensional electron and hole gases in undoped GaN quantum wells, created by built-in polarization fields and favorable band offsets. These interfacial states are essential for many high-power and high-frequency devices, yet momentum-resolved measurements (particularly under applied bias) remain rare due to two challenges: (i) the surface sensitivity of conventional vacuum-ultraviolet ARPES, which cannot probe deeply buried states, and (ii) the difficulty of implementing electrostatic gating in semiconductor heterostructures due to leakage currents. Here, we use soft X-ray ARPES to overcome the first challenge, directly accessing quantized states several nanometers below the surface in GaN/AlN heterostructures and relating their subband dispersions to transport characteristics. As a precursor to gated ARPES, we employ controlled oxygen adsorption to chemically tune the potential and track the resulting band shifts. This approach opens a pathway toward fully gate-tunable, momentum-resolved studies of buried states in wide-bandgap devices.</p>

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Momentum space imaging reveals chemical gating of 2D electron and hole gases in nitride heterostructures

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年5月31日

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  • E. Della Valle,
  • T.-S. Nguyen,
  • Z. Zhang,
  • Z. He,
  • N. Pieczulewski,
  • P. Constantinou,
  • C. Chang,
  • T. Schmitt,
  • H. G. Xing,
  • D. A. Muller,
  • G. Khalsa,
  • D. Jena,
  • V. N. Strocov

摘要

Gallium nitride (GaN) and aluminum nitride (AlN) host high-density two-dimensional electron and hole gases in undoped GaN quantum wells, created by built-in polarization fields and favorable band offsets. These interfacial states are essential for many high-power and high-frequency devices, yet momentum-resolved measurements (particularly under applied bias) remain rare due to two challenges: (i) the surface sensitivity of conventional vacuum-ultraviolet ARPES, which cannot probe deeply buried states, and (ii) the difficulty of implementing electrostatic gating in semiconductor heterostructures due to leakage currents. Here, we use soft X-ray ARPES to overcome the first challenge, directly accessing quantized states several nanometers below the surface in GaN/AlN heterostructures and relating their subband dispersions to transport characteristics. As a precursor to gated ARPES, we employ controlled oxygen adsorption to chemically tune the potential and track the resulting band shifts. This approach opens a pathway toward fully gate-tunable, momentum-resolved studies of buried states in wide-bandgap devices.