In a groundbreaking advancement poised to reshape the landscape of semiconductor technology, researchers have successfully demonstrated high-mobility hole transport in gallium nitride (GaN), revealing quantum oscillations previously unobserved in this material. Gallium nitride, a wide-bandgap semiconductor celebrated for its pivotal role in solid-state lighting and robust radio frequency devices, has long been hindered by the inefficiencies tied to hole doping and the notably low mobility of holes. This technical barrier has constrained in-depth explorations into the valence band properties and imperiled efforts to engineer hole-based transport mechanisms essential for innovative electronic applications.
The newly reported study navigates these challenges by harnessing a two-dimensional hole gas (2DHG) induced through polarization effects at the gallium nitride/aluminium nitride (AlN) interface. This interface technique leverages inherent material polarization to accumulate holes without relying on traditional doping methods, thereby circumventing typical doping inefficiencies that plague p-type GaN. Remarkably, the study reveals that these holes sufficiently populate two distinct valence bands within GaN—the light-hole and heavy-hole bands—achieving substantial mobilities of approximately 2,000 cm² V⁻¹ s⁻¹ and 400 cm² V⁻¹ s⁻¹ respectively at the cryogenic temperature of 2 K.
Central to this discovery is the observation of Shubnikov–de Haas (SdH) oscillations, quantum oscillations in electrical resistance that serve as precise probes into the Fermi surfaces and scattering mechanisms of charge carriers. The detection of SdH oscillations in both the light-hole and heavy-hole bands marks a pivotal advancement, confirming the degenerately occupied nature of these valence bands under cryogenic conditions. Through meticulous analysis of oscillation frequencies, the researchers extracted detailed insights into the sheet carrier densities and quantum scattering times related to both hole populations, further enriching the understanding of hole dynamics in GaN-based heterostructures.
Extracting the effective masses of the holes residing in these valence bands, the study provides key parameters that govern charge transport. The light holes, characterized by their smaller effective mass, inherently facilitate higher mobilities, while the heavy holes contribute a complementary transport channel albeit with lower mobility. This dual-band occupancy underscores the complex valence band structure governing hole conduction in GaN and offers a nuanced framework to engineer hole transport with tailored properties.
From a materials engineering perspective, the utilization of polarization-induced charge accumulation sidesteps the shortcomings of conventional acceptor doping strategies. Traditional substitutional doping in GaN often results in deep acceptor levels and poor activation efficiency, suppressing hole concentration and mobility. The polarization approach ingeniously exploits spontaneous and piezoelectric polarizations intrinsic to the heterointerface, creating a robust hole gas with high carrier density and mobility without introducing significant impurity scattering centers.
This pioneering achievement resonates beyond fundamental physics, heralding transformative implications for the burgeoning field of gallium nitride electronics. The demonstration of high-mobility two-dimensional holes opens pathways for developing complementary metal–oxide–semiconductor (CMOS) technology fully based on GaN, a longstanding pursuit challenged by the absence of efficient p-type conduction. Such CMOS integration promises enhanced power efficiency, high-frequency operation, and thermal stability, attributes vital for advanced electronics and high-performance computing systems.
Moreover, the cryogenic mobility enhancement reported in the study aligns seamlessly with emerging technological realms such as quantum computing. GaN-based devices with tailored hole transport properties could serve as the foundation for control electronics operating at ultra-low temperatures, optimizing coherence times and noise suppression critical for quantum information processors. The dual-band hole system, precisely characterized via quantum oscillatory phenomena, provides an exquisite testbed for exploring novel spin and charge interactions at the quantum level.
The research intricately combines high-quality GaN/AlN heterostructure fabrication with low-temperature magnetotransport measurements, revealing the interplay of two-dimensional quantum confinement and valence band physics. The clarity and reproducibility of the SdH oscillations not only validate the exceptional quality of the interface but also showcase the robustness of hole conduction channels under strong magnetic fields. These insights are instrumental for future device architectures targeting high-speed, low-noise, and energy-efficient operation.
Furthermore, the effective mass determination derived from the quantum oscillations offers a crucial parameter for theoretical modeling and device simulation. Accurate knowledge of hole effective masses underpins the design of GaN-based transistors, optoelectronic components, and spintronics applications. The distinct masses of the light and heavy hole bands enrich the modeling complexity but simultaneously allow for tailored engineering of devices exploiting anisotropic transport properties.
As technological demands push for miniaturization and higher performance, understanding and controlling hole transport in wide-bandgap semiconductors gains paramount importance. This work, by revealing the high mobilities achievable in a two-dimensional hole gas at the GaN/AlN interface, paves the way for innovative device concepts, including high-electron-mobility transistors (HEMTs) with complementary hole channels, hybrid quantum devices, and advanced sensors operating under extreme conditions.
The implications of this research extend to the broader semiconductor community, offering a template for engineering positive charge carriers in materials historically dominated by electron transport. Exploring polarization-induced phenomena to generate and manipulate holes could be translatable to other III-nitride compounds and layered heterostructures, fostering a new class of multifunctional electronic and photonic devices.
Finally, by bridging the gap between fundamental quantum transport studies and application-driven materials engineering, this study marks a seminal contribution to the field of semiconductor research. The convergence of high mobility, quantum oscillatory behavior, and two-dimensional hole gas formation in GaN not only enriches scientific knowledge but also equips technologists with the tools to push GaN-based technologies into realms previously inaccessible due to material limitations.
With this transformative understanding, the once elusive quantum oscillations of holes in p-type GaN come into clear focus, unlocking vast potential for next-generation electronics and quantum technologies. The study heralds a new era where gallium nitride’s full charge carrier repertoire can be leveraged, sculpting a future of unprecedented performance and innovation in electronic materials.
Subject of Research: High-mobility holes and quantum oscillations in gallium nitride (GaN) heterostructures.
Article Title: High-mobility holes in gallium nitride and their quantum oscillations.
Article References:
Chang, C.F.C., Dill, J.E., Zhang, Z. et al. High-mobility holes in gallium nitride and their quantum oscillations. Nat Electron (2026). https://doi.org/10.1038/s41928-026-01590-8
Image Credits: AI Generated
