III-nitride heterostructure field-effect transistors grown on semi-insulating GaN substrate without regrowth interface charge

Abstract

Charge is observed at the regrowth interface for heterostructure field-effect transistors (HFETs) grown on semi-insulating (SI) bulk GaN substrates, even with Fe doping in the regrown buffer layer for reduction of the interface charge. Ultraviolet photoenhanced chemical (PEC) etching is used to treat the surface of SI bulk GaN substrates. Employing optimized etching conditions, a very smooth surface is achieved for the bulk GaN substrate after the etching. The charge at the regrowth interface is eliminated for HFETs grown on etched SI GaN substrates. Secondary ion mass spectrometry measurements show that the Si impurity concentration at the regrowth interface for HFETs grown on etched SI GaN substrates is much lower than that for HFETs grown on unetched SI GaN substrates, which suggests that the charge-containing layer on the SI substrate is removed by PEC etching and that the effects of the reduced charge layer near the regrowth interface can be eliminated by Fe doping for HFETs grown on etched SI substrates.

Dual temperature process for reduction in regrowth interfacial charge in AlGaN/GaN HEMTs grown on GaN substrates

“…Liu et. al reported that UV photoenhanced chemical etching of the GaN substrates reduced the concentration of Si at the interface, but did not completely eliminate it [3]. As a result, impurities including Fe [3,4], C [2] and Mg [5] have been added to compensate the remaining Si donors.…”

Physical Properties of AlGaN/GaN Heterostructures Grown on Vicinal Substrates

“…The same CV measurements showed a free carrier concentration >10 18 cm À3 in the first 20 nm of the substrate. [24][25][26] Secondary-ion mass spectroscopy (SIMS) measurements of AlGaN/GaN heterostructures on representative semi-insulating bulk GaN substrates confirmed the atomic silicon concentration, [Si], to be >10 19 cm À3 at the bulk GaNepitaxial interface. Areal silicon concentration, [Si] areal , at the bulk GaN-epitaxial interface was determined to be 1.6 9 10 14 cm À2 .…”

AlGaN-Based Lateral Current Injection Laser Diodes Using Regrown Ohmic Contacts

“…Unlike n-type AlGaN, regrowth of p-type AlGaN may be very difficult in the presence of incidental silicon delta doping at the regrowth interface [8], but this issue does not appear to be fundamental. Various approaches are reported in the literature to suppress Si spikes [8], [9]. This article presents a 290 nm UV edge emitting LCI LD design using polarization charge matched quaternary QWBs and regrown Ohmic contacts.…”

“…Besides, it offers smooth transition from regrown Ohmic region to the as-grown epitaxial layers [7]. Unlike n-type AlGaN, regrowth of p-type AlGaN may be very difficult in the presence of incidental silicon delta doping at the regrowth interface [8], but this issue does not appear to be fundamental. Various approaches are reported in the literature to suppress Si spikes [8], [9].…”