Studies on the influences of i-GaN, n-GaN, p-GaN and InGaN cap layers in AlGaN/GaN high-electron-mobility transistors

Subramaniam Arulkumaran, Takashi Egawa, Hiroyasu Ishikawa

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31 Citations (Scopus)

Abstract

Systematic studies were performed on the influence of different cap layers of i-GaN, n-GaN, p-GaN and InGaN on AlGaN/ GaN high-electron-mobility transistors (HEMTs) grown on sapphire by metal organic chemical vapor deposition. The decrease of maximum extrinsic transconductance (g m) and maximum drain current density (I Dmax) values agrees with the product values of two-dimensional electron gas (2DEG) mobility (μ H) and 2DEG sheet concentration (n s) of AlGaN/GaN HEMT structures. An improved Schottky barrier height with low surface roughness has been observed in AlGaN/GaN HEMT structure with i-GaN and n-GaN cap layers. The HEMTs with i-GaN cap layer exhibited low gate leakage current with high breakdown voltage among the other HEMTs. Though the HEMTs with n-GaN cap layer and without cap layers exhibited good μ H, g m, I Dmax values, the ac characteristics are not up to the extent of HEMTs with i-GaN cap layer. All the devices except the HEMTs with InGaN cap layers were operational even up to the measurement temperature of 350°C. The HEMTs with i-GaN cap layer exhibited collapse-free I DS-V DS characteristics with small I D hysteresis width variations among the other HEMTs. The observation of small threshold voltage variation, small drain current hysteresis width and small white light illumination effects confirms the existence of small trapping effects in HEMTs with i-GaN cap layers. Only one thermally activated trap level at -0.161 eV was observed on AlGaN/GaN HEMTs with i-GaN cap layer. However, each of the three trap levels has been observed in HEMTs with other cap layers and HEMTs without cap layers. From this, it is concluded that the collapse-related traps are screened/passivated from two-dimensional electron gas by the addition of thin i-GaN cap layer on AlGaN/GaN HEMTs. The cap layer i-GaN (3 nm) is a promising candidate to get collapse-free AlGaN/GaN HEMTs.

Original languageEnglish
Pages (from-to)2953-2960
Number of pages8
JournalJapanese Journal of Applied Physics, Part 1: Regular Papers and Short Notes and Review Papers
Volume44
Issue number5 A
DOIs
Publication statusPublished - 2005 May
Externally publishedYes

Fingerprint

High electron mobility transistors
high electron mobility transistors
caps
Two dimensional electron gas
Drain current
traps
electron gas
Hysteresis
hysteresis
Organic chemicals
Transconductance
transconductance
Electric breakdown
Threshold voltage
electrical faults
Sapphire
Temperature measurement
Leakage currents
threshold voltage
metalorganic chemical vapor deposition

Keywords

  • Activation energy
  • AlGaN/GaN
  • Breakdown voltage
  • Cap layer
  • Collapse-related traps
  • Current collapse
  • GaN
  • HEMT
  • Illumination
  • InGaN

ASJC Scopus subject areas

  • Physics and Astronomy (miscellaneous)

Cite this

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title = "Studies on the influences of i-GaN, n-GaN, p-GaN and InGaN cap layers in AlGaN/GaN high-electron-mobility transistors",
abstract = "Systematic studies were performed on the influence of different cap layers of i-GaN, n-GaN, p-GaN and InGaN on AlGaN/ GaN high-electron-mobility transistors (HEMTs) grown on sapphire by metal organic chemical vapor deposition. The decrease of maximum extrinsic transconductance (g m) and maximum drain current density (I Dmax) values agrees with the product values of two-dimensional electron gas (2DEG) mobility (μ H) and 2DEG sheet concentration (n s) of AlGaN/GaN HEMT structures. An improved Schottky barrier height with low surface roughness has been observed in AlGaN/GaN HEMT structure with i-GaN and n-GaN cap layers. The HEMTs with i-GaN cap layer exhibited low gate leakage current with high breakdown voltage among the other HEMTs. Though the HEMTs with n-GaN cap layer and without cap layers exhibited good μ H, g m, I Dmax values, the ac characteristics are not up to the extent of HEMTs with i-GaN cap layer. All the devices except the HEMTs with InGaN cap layers were operational even up to the measurement temperature of 350°C. The HEMTs with i-GaN cap layer exhibited collapse-free I DS-V DS characteristics with small I D hysteresis width variations among the other HEMTs. The observation of small threshold voltage variation, small drain current hysteresis width and small white light illumination effects confirms the existence of small trapping effects in HEMTs with i-GaN cap layers. Only one thermally activated trap level at -0.161 eV was observed on AlGaN/GaN HEMTs with i-GaN cap layer. However, each of the three trap levels has been observed in HEMTs with other cap layers and HEMTs without cap layers. From this, it is concluded that the collapse-related traps are screened/passivated from two-dimensional electron gas by the addition of thin i-GaN cap layer on AlGaN/GaN HEMTs. The cap layer i-GaN (3 nm) is a promising candidate to get collapse-free AlGaN/GaN HEMTs.",
keywords = "Activation energy, AlGaN/GaN, Breakdown voltage, Cap layer, Collapse-related traps, Current collapse, GaN, HEMT, Illumination, InGaN",
author = "Subramaniam Arulkumaran and Takashi Egawa and Hiroyasu Ishikawa",
year = "2005",
month = "5",
doi = "10.1143/JJAP.44.2953",
language = "English",
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pages = "2953--2960",
journal = "Japanese Journal of Applied Physics, Part 1: Regular Papers & Short Notes",
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TY - JOUR

T1 - Studies on the influences of i-GaN, n-GaN, p-GaN and InGaN cap layers in AlGaN/GaN high-electron-mobility transistors

AU - Arulkumaran, Subramaniam

AU - Egawa, Takashi

AU - Ishikawa, Hiroyasu

PY - 2005/5

Y1 - 2005/5

N2 - Systematic studies were performed on the influence of different cap layers of i-GaN, n-GaN, p-GaN and InGaN on AlGaN/ GaN high-electron-mobility transistors (HEMTs) grown on sapphire by metal organic chemical vapor deposition. The decrease of maximum extrinsic transconductance (g m) and maximum drain current density (I Dmax) values agrees with the product values of two-dimensional electron gas (2DEG) mobility (μ H) and 2DEG sheet concentration (n s) of AlGaN/GaN HEMT structures. An improved Schottky barrier height with low surface roughness has been observed in AlGaN/GaN HEMT structure with i-GaN and n-GaN cap layers. The HEMTs with i-GaN cap layer exhibited low gate leakage current with high breakdown voltage among the other HEMTs. Though the HEMTs with n-GaN cap layer and without cap layers exhibited good μ H, g m, I Dmax values, the ac characteristics are not up to the extent of HEMTs with i-GaN cap layer. All the devices except the HEMTs with InGaN cap layers were operational even up to the measurement temperature of 350°C. The HEMTs with i-GaN cap layer exhibited collapse-free I DS-V DS characteristics with small I D hysteresis width variations among the other HEMTs. The observation of small threshold voltage variation, small drain current hysteresis width and small white light illumination effects confirms the existence of small trapping effects in HEMTs with i-GaN cap layers. Only one thermally activated trap level at -0.161 eV was observed on AlGaN/GaN HEMTs with i-GaN cap layer. However, each of the three trap levels has been observed in HEMTs with other cap layers and HEMTs without cap layers. From this, it is concluded that the collapse-related traps are screened/passivated from two-dimensional electron gas by the addition of thin i-GaN cap layer on AlGaN/GaN HEMTs. The cap layer i-GaN (3 nm) is a promising candidate to get collapse-free AlGaN/GaN HEMTs.

AB - Systematic studies were performed on the influence of different cap layers of i-GaN, n-GaN, p-GaN and InGaN on AlGaN/ GaN high-electron-mobility transistors (HEMTs) grown on sapphire by metal organic chemical vapor deposition. The decrease of maximum extrinsic transconductance (g m) and maximum drain current density (I Dmax) values agrees with the product values of two-dimensional electron gas (2DEG) mobility (μ H) and 2DEG sheet concentration (n s) of AlGaN/GaN HEMT structures. An improved Schottky barrier height with low surface roughness has been observed in AlGaN/GaN HEMT structure with i-GaN and n-GaN cap layers. The HEMTs with i-GaN cap layer exhibited low gate leakage current with high breakdown voltage among the other HEMTs. Though the HEMTs with n-GaN cap layer and without cap layers exhibited good μ H, g m, I Dmax values, the ac characteristics are not up to the extent of HEMTs with i-GaN cap layer. All the devices except the HEMTs with InGaN cap layers were operational even up to the measurement temperature of 350°C. The HEMTs with i-GaN cap layer exhibited collapse-free I DS-V DS characteristics with small I D hysteresis width variations among the other HEMTs. The observation of small threshold voltage variation, small drain current hysteresis width and small white light illumination effects confirms the existence of small trapping effects in HEMTs with i-GaN cap layers. Only one thermally activated trap level at -0.161 eV was observed on AlGaN/GaN HEMTs with i-GaN cap layer. However, each of the three trap levels has been observed in HEMTs with other cap layers and HEMTs without cap layers. From this, it is concluded that the collapse-related traps are screened/passivated from two-dimensional electron gas by the addition of thin i-GaN cap layer on AlGaN/GaN HEMTs. The cap layer i-GaN (3 nm) is a promising candidate to get collapse-free AlGaN/GaN HEMTs.

KW - Activation energy

KW - AlGaN/GaN

KW - Breakdown voltage

KW - Cap layer

KW - Collapse-related traps

KW - Current collapse

KW - GaN

KW - HEMT

KW - Illumination

KW - InGaN

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U2 - 10.1143/JJAP.44.2953

DO - 10.1143/JJAP.44.2953

M3 - Article

AN - SCOPUS:22544451237

VL - 44

SP - 2953

EP - 2960

JO - Japanese Journal of Applied Physics, Part 1: Regular Papers & Short Notes

JF - Japanese Journal of Applied Physics, Part 1: Regular Papers & Short Notes

SN - 0021-4922

IS - 5 A

ER -