Fabrication of p-channel heterostructure field effect transistors with polarization-induced two-dimensional hole gases at metal-polar GaN/AlInGaN interfaces

• Published in: Journal of physics. D, Applied physics Applied physics, 2014-04, Vol.47 (17), p.175103
• Main Authors: Reuters, B, Hahn, H, Pooth, A, Holländer, B, Breuer, U, Heuken, M, Kalisch, H, Vescan, A
• Format: Article
• Language: English
• Subjects: 2DHG; AlInGaN; enhancement mode; holes; InAlGaN; p-channel; p-type
• ISSN: 0022-3727; 1361-6463
• DOI: 10.1088/0022-3727/47/17/175103

Novel nitride-based heterostructures have been fabricated demonstrating two-dimensional hole gases as the basis for p-channel transistors. The carrier density in the 2DHG is adjusted between very high values of 2 × 1013 cm−2 and low values of 6 × 1011 cm−2 by the polarization difference, ΔP, between quaternary AlInGaN backbarriers and a GaN channel on top. Record mobilities for holes in GaN of 43 cm2 V−1 s−1 (median 30 cm2 V−1 s−1) are observed for a moderate 2DHG density of 1.3 × 1012 cm−2 (median 2.2 × 1012 cm−2). Heterostructures with different backbarrier compositions are processed to field effect transistors and show a systematic threshold voltage shift from positive to negative values according to the corresponding 2DHG density. It is shown for the first time that by appropriate polarization-engineering through changing the AlInGaN composition, both depletion and enhancement mode behaviour can be achieved for p-channel devices. Drain current densities |Id| above 40 mA mm−1 at a drain source voltage Vds of −10 V are achieved for heterostructures with high polarization differences, ΔP, between AlInGaN backbarrier and GaN channel. Reducing ΔP leads to decreasing on-state drain currents |Id| with a simultaneous reduction in off-state current. This results in very large on/off ratios of up to 108 for enhancement mode devices, demonstrating record performances and great potential for future applications.