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

Abstract

The effects of growth temperature and Mg compensation doping on the structural and electrical properties of AlGaN/AlN/GaN high electron mobility transistor (HEMTs) structures grown on low threading dislocation density bulk GaN substrates by metalorganic chemical vapor deposition were investigated. The background electron concentration in the regrown GaN was found to decrease from 1.5x1018 cm‐3 to 2x1016 cm‐3 as the growth temperature was reduced from 1100 °C to 950 °C. A dual temperature process was then employed for growth of the GaN base layer and AlGaN/AlN/GaN top heterostructure in the HEMT along with Mg doping of the GaN base to compensate residual Si donors at the regrown interface. Using this approach, AlGaN/AlN/GaN HEMTs were produced that had a sheet carrier density as high as 1.1x1013 cm‐3 with a room temperature mobility of 1600 cm2/Vs. The incorporation of a thin AlN layer at the regrown interface was found to reduce the sheet carrier density of the overall structure (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Abnormal increase of 2DEG density in AlGaN/GaN HEMT grown on free-standing GaN substrate

“…At present, it is believed that the reason for the increase of 2DEG density in the AlGaN/GaN HEMT structures grown on GaN substrates is related to Si impurities. 8,9,11,13) In this study, we observed a decrease of the 2DEG mobility due to an abnormal increase of the 2DEG density. The latter was caused by a donor with thermal ionization energy around 67.8 meV, the donor is not Si but N vacancy.…”

“…8) Eichfeld et al found that the number of redundant electrons could be reduced by introducing compensation doping and an AlN layer at the growth interface of the GaN substrate. 9) Generally, the GaN substrates easily adsorb donor impurities such as C, O, and Si from chemical-mechanical polishing processes and the atmospheric environment. However, Si impurities are more difficult to remove completely by substrate-cleaning methods such as chemical etching and in situ heat treatment than are C or O.…”

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.…”

2 W mm−1 power density of an AlGaN/GaN HEMT grown on free-standing GaN substrate at 40 GHz

“…In this paper, the device is fabricated on AlGaN/GaN epilayer grown by metal organic chemical vapor deposition (MOCVD) on hydride vapor phase epitaxy (HVPE) commercial free-standing gallium nitride (GaN) substrate. This structure presents the advantages of the direct growth of high crystalline quality GaN with threading dislocation density below 10 7 cm −2 [5,6]. The goal of this study is to demonstrate the high microwave power performance at 40 GHz of HEMTs on GaN substrate.…”