Optimization of Fe doping at the regrowth interface of GaN for applications to III-nitride-based heterostructure field-effect transistors

Abstract

The authors have studied the effects of Fe doping at the interface between GaN epitaxial layers for heterostructure field-effect transistors grown by metal-organic chemical vapor deposition and the corresponding impact on the device characteristics. The epitaxial structures were grown with different Fe-doped GaN layers at the layer-template interface. Analysis of the measured electron and interface charge distributions in the heterostructures demonstrated the important role of Fe doping at the regrowth interface. No charge at the regrowth interface was observed in transistor structures with a thick Fe-doped layer. Characterization of the electrical properties of the transistor structures revealed the presence of high sheet carrier concentrations and improved mobilities with increasing thickness of the Fe-doped GaN layer at the regrowth interface.

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

“…Using this approach, AlGaN/AlN/GaN HEMTs were produced that had a sheet carrier density as high as 1.1x10 13 cm -3 with a room temperature mobility of 1600 cm 1 Introduction AlGaN/GaN high electron mobility transistors (HEMTs) on low threading dislocation (TD) density GaN substrates are being explored for their use in high power, high frequency devices. One of the challenges encountered in GaN homoepitaxy is the incorporation of residual impurities including C, O and Si at the regrown interface which can introduce additional charge carriers into the device structure [1]. Prior studies have demonstrated that the O and C impurities can be effectively eliminated through pre-growth thermal treatment in both metalorganic chemical vapor deposition (MOCVD) [1] and molecular beam epitaxy (MBE) [2]; however, the Si was not significantly reduced by this process.…”

“…One of the challenges encountered in GaN homoepitaxy is the incorporation of residual impurities including C, O and Si at the regrown interface which can introduce additional charge carriers into the device structure [1]. Prior studies have demonstrated that the O and C impurities can be effectively eliminated through pre-growth thermal treatment in both metalorganic chemical vapor deposition (MOCVD) [1] and molecular beam epitaxy (MBE) [2]; however, the Si was not significantly reduced by this process. Liu et.…”

Surface treatment on the growth surface of semi‐insulating GaN bulk substrate for III‐nitride heterostructure field‐effect transistors

“…Such growth interface generally contains impurities such as Si, O, and C, which may induce the additional charge layers near the interface. Authors previously showed that optimized Fe doping can remove the additional charge at the re-growth interface of a HFET structure grown on a GaN template/sapphire substrate [7] but optimized Fe doping was not enough to remove the interface charge for HFETs on SI-GaN substrates [8]. The difference between re-growth interface of GaN template on sapphire substrate and growth interface of SI-GaN substrate, and the origin of additional charge from HFET on SI-GaN bulk substrate are not fully understood.…”

Scanning capacitance microscopy as a tool for the assessment of unintentional doping in GaN

“…1 Introduction The control of unintentional doping in GaN has been shown to be an important issue in the optimization of III-nitride-based heterostructure field-effect transistors [1]. Iron doping can be used to eliminate unintentional conductivity, producing semi-insulating material [2], but, to optimise this approach, the location of the ironcontaining material should ideally be matched to the location of the unintentionally doped (uid) region or regions in the GaN.…”