PMID- 37666104
OWN - NLM
STAT- PubMed-not-MEDLINE
LR  - 20230916
IS  - 1879-2723 (Electronic)
IS  - 0304-3991 (Linking)
VI  - 254
DP  - 2023 Dec
TI  - Scanning capacitance microscopy of GaN-based high electron mobility transistor 
      structures: A practical guide.
PG  - 113833
LID - S0304-3991(23)00150-X [pii]
LID - 10.1016/j.ultramic.2023.113833 [doi]
AB  - The scanning capacitance microscope (SCM) is a powerful tool to characterise 
      local electrical properties in GaN-based high electron mobility transistor (HEMT) 
      structures with nanoscale resolution. We investigated the experimental setup and 
      the imaging conditions to optimise the SCM contrast. As to the experimental 
      setup, we show that the desired tip should be sharp (e.g., with the tip radius of 
      </=25nm) and its coating should be made of conductive doped diamond. Most 
      importantly, its spring constant should be large to achieve stable tip-sample 
      contact. The selected tip should be positioned close to both the edge and Ohmic 
      contact of the sample. Regarding the imaging conditions, we also show that a dc 
      bias should be applied in addition to an ac bias because the latter alone is not 
      sufficient to deplete the two-dimensional electron gas (2DEG) in the AlGaN/GaN 
      heterostructure. The approximate range of the effective dc bias values was found 
      by measuring the local dC/dV-V curves, yielding, after further optimisation, two 
      optimised dc bias values which provide strong, but opposite, SCM contrast. In 
      comparison, the selected ac bias value has no significant impact on the SCM 
      contrast. The described methodology could potentially also be applied to other 
      types of HEMT structures, and highly-doped samples.
CI  - Copyright (c) 2023 The Author(s). Published by Elsevier B.V. All rights reserved.
FAU - Chen, Chen
AU  - Chen C
AD  - Department of Materials Science and Metallurgy, University of Cambridge, 
      Cambridge CB3 0FS, United Kingdom. Electronic address: cc2053@cam.ac.uk.
FAU - Ghosh, Saptarsi
AU  - Ghosh S
AD  - Department of Materials Science and Metallurgy, University of Cambridge, 
      Cambridge CB3 0FS, United Kingdom.
FAU - Adams, Francesca
AU  - Adams F
AD  - Department of Materials Science and Metallurgy, University of Cambridge, 
      Cambridge CB3 0FS, United Kingdom.
FAU - Kappers, Menno J
AU  - Kappers MJ
AD  - Department of Materials Science and Metallurgy, University of Cambridge, 
      Cambridge CB3 0FS, United Kingdom.
FAU - Wallis, David J
AU  - Wallis DJ
AD  - Department of Materials Science and Metallurgy, University of Cambridge, 
      Cambridge CB3 0FS, United Kingdom; Centre for High Frequency Engineering, 
      University of Cardiff, Cardiff CF24 3AA, United kingdom.
FAU - Oliver, Rachel A
AU  - Oliver RA
AD  - Department of Materials Science and Metallurgy, University of Cambridge, 
      Cambridge CB3 0FS, United Kingdom.
LA  - eng
PT  - Journal Article
DEP - 20230822
PL  - Netherlands
TA  - Ultramicroscopy
JT  - Ultramicroscopy
JID - 7513702
SB  - IM
OTO - NOTNLM
OT  - High electron mobility transistor structures
OT  - Plan-view characterisation
OT  - Scanning capacitance microscopy
COIS- Declaration of competing interest The authors declare that they have no known 
      competing financial interests or personal relationships that could have appeared 
      to influence the work reported in this paper.
EDAT- 2023/09/05 00:42
MHDA- 2023/09/05 00:43
CRDT- 2023/09/04 18:07
PHST- 2022/12/02 00:00 [received]
PHST- 2023/07/12 00:00 [revised]
PHST- 2023/08/17 00:00 [accepted]
PHST- 2023/09/05 00:43 [medline]
PHST- 2023/09/05 00:42 [pubmed]
PHST- 2023/09/04 18:07 [entrez]
AID - S0304-3991(23)00150-X [pii]
AID - 10.1016/j.ultramic.2023.113833 [doi]
PST - ppublish
SO  - Ultramicroscopy. 2023 Dec;254:113833. doi: 10.1016/j.ultramic.2023.113833. Epub 
      2023 Aug 22.