High electron mobility recovery in AlGaN/GaN 2DEG channels regrown on etched surfaces

Abstract

This paper reports high two-dimensional electron gas mobility attained from the regrowth of the AlGaN gating layer on ex situ GaN surfaces. To repair etch-damaged GaN surfaces, various pretreatments were conducted via metalorganic chemical vapor deposition, followed by a regrown AlGaN/GaN mobility test structure to evaluate the extent of recovery. The developed treatment process that was shown to significantly improve the electron mobility consisted of a N 2 +NH 3 pre-anneal plus an insertion of a 4 nm or thicker GaN interlayer prior to deposition of the AlGaN gating layer. Using the optimized process, a high electron mobility transistor (HEMT) device was fabricated which exhibited a high mobility of 1450 cm 2 V −1 s −1 (R sh =574 ohm/sq) and low dispersion characteristics. The additional inclusion of an in situ Al 2 O 3 dielectric into the regrowth process for MOS-HEMTs still preserved the transport properties near etch-impacted areas.

Etched-And-Regrown GaN P–N Diodes with Low-Defect Interfaces Prepared by In Situ TBCl Etching

“…Implant- and diffusion-based selective-area doping (SAD) methods have been actively investigated, − and each faces its respective challenges. Selective-area etching of GaN followed by regrowth or selective-area growth − is intuitively straightforward but has been hampered by the damage and contamination incurred during conventional inductively coupled plasma (ICP) etching. − In the context of etch-and-regrowth, several groups have developed processes to mitigate or repair ICP etching damage with promising results. − Recently, we reported an alternative, in situ etching of GaN with the use of tertiarybutylchloride (TBCl), a Cl-based organometallic precursor. Initial findings indicated that the TBCl etching of GaN has a sufficiently high etch rate and produces minimal damage or contamination. , This etching technique, however, has yet to be tested in working GaN electronic devices.…”

Collision-dominated conductance in clean two-dimensional metals

“…Recent experiments on suspended single layergraphene [1][2][3] and on conventional two-dimensional electron gases (2DEG) [4][5][6][7][8][9] have reached very high levels of purity and thus high mobilities. This has raised interesting questions as to the role of electron-electron interactions in such systems, especially in Dirac or Weyl materials such as graphene, as well as in other ultraclean 2D (semi)metals.…”

Temperature dependence on plasma-induced damage and chemical reactions in GaN etching processes using chlorine plasma

“…4) Since etched surfaces are annealed under N 2 and NH 3 mixture and then regrown by metalorganic chemical vapor deposition, leading to recovery of high electron mobility of the two-dimensional electron gas (2DEG), the process needs temperatures higher than 800 °C with 950 °C as the maximum. 23) To reduce PID, high-temperature Cl 2 plasma etching of GaN has been studied. 24) The etch by-products of the Cl 2 plasma etching of GaN are GaCl 3 , NCl 3 , and N 2 , among others.…”