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Title: The mechanism for polarity inversion of GaN via a thin AlN layer: direct experimental evidence

Abstract

Lateral-polarity heterostructures of GaN on c-sapphire were prepared by deposition and patterning of a thin low-temperature AlN nucleation layer. Adjacent macroscopic domains were found to have opposite polarity; domains grown on the AlN nucleation layer were Ga-polar while those grown on the nitrided sapphire were N-polar, as confirmed by convergent-beam electron diffraction and Z- contrast images. We directly determined the atomic interface structure between the AlN and c-sapphire with an aberration-corrected scanning transmission electron microscope at ~1.0 resolution. This is the direct experimental evidence for the origin of the polarity control in III-nitrides. This understanding is an important step toward manipulating polarity in these semiconductors.

Authors:
 [1];  [2];  [3];  [3];  [1];  [1]
  1. ORNL
  2. National Renewable Energy Laboratory (NREL)
  3. North Carolina State University
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
1081598
DOE Contract Number:
DE-AC05-00OR22725
Resource Type:
Journal Article
Resource Relation:
Journal Name: Applied Physics Letters; Journal Volume: 91; Journal Issue: 203115
Country of Publication:
United States
Language:
English

Citation Formats

Pennycook, Stephen J, Liu, Ford, Collazo, Ramon, Mita, Seiji, Sitar, Zlatko, and Duscher, Gerd J M. The mechanism for polarity inversion of GaN via a thin AlN layer: direct experimental evidence. United States: N. p., 2007. Web.
Pennycook, Stephen J, Liu, Ford, Collazo, Ramon, Mita, Seiji, Sitar, Zlatko, & Duscher, Gerd J M. The mechanism for polarity inversion of GaN via a thin AlN layer: direct experimental evidence. United States.
Pennycook, Stephen J, Liu, Ford, Collazo, Ramon, Mita, Seiji, Sitar, Zlatko, and Duscher, Gerd J M. Mon . "The mechanism for polarity inversion of GaN via a thin AlN layer: direct experimental evidence". United States. doi:.
@article{osti_1081598,
title = {The mechanism for polarity inversion of GaN via a thin AlN layer: direct experimental evidence},
author = {Pennycook, Stephen J and Liu, Ford and Collazo, Ramon and Mita, Seiji and Sitar, Zlatko and Duscher, Gerd J M},
abstractNote = {Lateral-polarity heterostructures of GaN on c-sapphire were prepared by deposition and patterning of a thin low-temperature AlN nucleation layer. Adjacent macroscopic domains were found to have opposite polarity; domains grown on the AlN nucleation layer were Ga-polar while those grown on the nitrided sapphire were N-polar, as confirmed by convergent-beam electron diffraction and Z- contrast images. We directly determined the atomic interface structure between the AlN and c-sapphire with an aberration-corrected scanning transmission electron microscope at ~1.0 resolution. This is the direct experimental evidence for the origin of the polarity control in III-nitrides. This understanding is an important step toward manipulating polarity in these semiconductors.},
doi = {},
journal = {Applied Physics Letters},
number = 203115,
volume = 91,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 2007},
month = {Mon Jan 01 00:00:00 EST 2007}
}
  • AlN/GaN high electron mobility transistor (HEMT) structures with thin GaN/AlN buffer layer have been analyzed theoretically and experimentally, and the effects of the AlN barrier and GaN buffer layer thicknesses on two-dimensional electron gas (2DEG) density and transport properties have been evaluated. HEMT structures consisting of [300 nm GaN/ 200 nm AlN] buffer layer on sapphire were grown by plasma-assisted molecular beam epitaxy and exhibited a remarkable agreement with the theoretical calculations, suggesting a negligible influence of the crystalline defects that increase near the heteroepitaxial interface. The 2DEG density varied from 6.8 × 10{sup 12} to 2.1 × 10{sup 13} cm{sup −2} as themore » AlN barrier thickness increased from 2.2 to 4.5 nm, while a 4.5 nm AlN barrier would result to 3.1 × 10{sup 13} cm{sup −2} on a GaN buffer layer. The 3.0 nm AlN barrier structure exhibited the highest 2DEG mobility of 900 cm{sup 2}/Vs for a density of 1.3 × 10{sup 13} cm{sup −2}. The results were also confirmed by the performance of 1 μm gate-length transistors. The scaling of AlN barrier thickness from 1.5 nm to 4.5 nm could modify the drain-source saturation current, for zero gate-source voltage, from zero (normally off condition) to 0.63 A/mm. The maximum drain-source current was 1.1 A/mm for AlN barrier thickness of 3.0 nm and 3.7 nm, and the maximum extrinsic transconductance was 320 mS/mm for 3.0 nm AlN barrier.« less
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