Study on growth and electrical performance of double‐heterostructure AlGaN/GaN/AlGaN field‐effect‐transistors

Abstract

Device simulations and first experimental results on double‐heterostructure (DH) AlGaN/GaN/AlGaN field effect transistors are presented. Simulations show that above an Al content of approximately 10% in the back GaN/AlGaN barrier, a hole channel could be formed. On the other hand the DH is shown to reduce the electric field in the regions adjacent to the channel and to suppress trapping. First experimental results confirm the existence of the 2‐dimensional electron gas for a back barrier Al content of 5%. The device performance although strongly limited by the material quality, is comparable to that of conventional structures, promising significant potential once design and material issues are resolved. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

AlN barrier HFETs with AlGaN channels to shift the threshold voltage to higher positive values: a proposal

“…Aspects regarding thermal conductivity should also be considered. Therefore, the principle of the double heterostructure (DH) which is necessary to form a DH field effect transistor (DHFET) is briefly discussed [47]. In GaN-based devices, AlGaN backbarriers with a typical Al content of 5-10% [47,48,8] instead of GaN buffers are introduced to form an energetic barrier which can be utilized to prevent a punch-through in the buffer [47].…”

Buffer-Related Degradation Aspects of Single and Double-Heterostructure Quantum Well InAlN/GaN High-Electron-Mobility Transistors

“…Moreover, besides the blocking effect of the back barrier on the injection of hot electrons, the increased E C À E F in the buffer layer of the DHQW HEMT increases the electron energy required for the dehydrogenation of point defects. 12) We note that to explain the observed changes in the studied HEMTs, alternative mechanisms related to the charging of pre-existing traps in the buffer 14,26) or at the surface of the barrier layer 27) may be considered. However, in our case, at least in a time scale of weeks, we observe irreversible effects, which is in contrast to the transient effects expected for a sole electron trapping.…”

“…12) A better confinement of electrons in the AlGaN/GaN HEMT channel and a reduced rate of carrier injection in the GaN buffer were observed for the double-heterostructure quantum well (DHQW) system by applying the AlGaN back barrier. 13,14) Consequently, a lower subthreshold drain leakage 13,14) and a reduced trapping in the buffer 14) could be obtained. The AlGaN back barrier has also been tested in InAlN/GaN HEMTs, resulting in an improved device RF performance and reduced short-channel effects.…”

Degradation Study of Single and Double-Heterojunction InAlN/GaN HEMTs by Two-Dimensional Simulation

“…The changes are irreversible and can lead to a shift in the threshold voltage and to degraded channel mobility. A better confinement of electrons in the AlGaN/GaN HEMT channel and a reduced rate of carrier injection in the GaN buffer were observed for the double-heterostructure quantum well (DHQW) system by applying an AlGaN back barrier [7,8]. Consequently, a lower sub-threshold drain leakage [7,8] and a reduced trapping in the buffer [8] could be obtained.…”

“…A better confinement of electrons in the AlGaN/GaN HEMT channel and a reduced rate of carrier injection in the GaN buffer were observed for the double-heterostructure quantum well (DHQW) system by applying an AlGaN back barrier [7,8]. Consequently, a lower sub-threshold drain leakage [7,8] and a reduced trapping in the buffer [8] could be obtained. The AlGaN back barrier has also been tested in InAlN/GaN HEMTs, resulting in an improved device RF performance and reduced short-channel effects [9].…”