TY - JOUR
T1 - Impact of nonpolar AlGaN quantum wells on deep ultraviolet laser diodes
AU - Kojima, K.
AU - Yamaguchi, A. A.
AU - Funato, M.
AU - Kawakami, Y.
AU - Noda, S.
N1 - Funding Information:
This work was supported by KAKENHI (21016006).
Copyright:
Copyright 2011 Elsevier B.V., All rights reserved.
PY - 2011/8/15
Y1 - 2011/8/15
N2 - The radiation properties of nonpolar AlGaN quantum wells (QWs) were theoretically investigated by comparing them to those of c-plane AlGaN QWs with heavy holes as the top valence band (VB). First, the conditions to minimize the threshold carrier density of c-plane QW laser diodes were explored. A thin well width (∼1 nm) and reduction of the Al content in the well layer were important to reduce threshold carrier density because narrow wells suppressed the quantum confined Stark effect and AlGaN with a lower Al content had a lower density of states. Moreover, the emission wavelength was widely controlled by tuning the Al contents of both the well and barrier layers under the proposed conditions. Then the properties of nonpolar AlGaN QWs were investigated. Nonpolar AlGaN had several superior characteristics compared to c-plane QWs, including large overlap integrals, optical polarization suitable for both edge and surface emissions, an almost linearly polarized optical dipole between the conduction band and top VB due to the isolated VBs, and a reduced VB density of state. Finally, the threshold carrier densities of both nonpolar and optimized c-plane QWs were compared as functions of the transition wavelength. At a given wavelength, the threshold of nonpolar QWs was lower than that of c-plane ones. Particularly below 260 nm, nonpolar QWs had a low threshold, whereas that of c-plane QWs drastically increased due to the large VB mass of AlN and carrier population in the crystal-field splitting band.
AB - The radiation properties of nonpolar AlGaN quantum wells (QWs) were theoretically investigated by comparing them to those of c-plane AlGaN QWs with heavy holes as the top valence band (VB). First, the conditions to minimize the threshold carrier density of c-plane QW laser diodes were explored. A thin well width (∼1 nm) and reduction of the Al content in the well layer were important to reduce threshold carrier density because narrow wells suppressed the quantum confined Stark effect and AlGaN with a lower Al content had a lower density of states. Moreover, the emission wavelength was widely controlled by tuning the Al contents of both the well and barrier layers under the proposed conditions. Then the properties of nonpolar AlGaN QWs were investigated. Nonpolar AlGaN had several superior characteristics compared to c-plane QWs, including large overlap integrals, optical polarization suitable for both edge and surface emissions, an almost linearly polarized optical dipole between the conduction band and top VB due to the isolated VBs, and a reduced VB density of state. Finally, the threshold carrier densities of both nonpolar and optimized c-plane QWs were compared as functions of the transition wavelength. At a given wavelength, the threshold of nonpolar QWs was lower than that of c-plane ones. Particularly below 260 nm, nonpolar QWs had a low threshold, whereas that of c-plane QWs drastically increased due to the large VB mass of AlN and carrier population in the crystal-field splitting band.
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U2 - 10.1063/1.3627180
DO - 10.1063/1.3627180
M3 - Article
AN - SCOPUS:80052418371
VL - 110
JO - Journal of Applied Physics
JF - Journal of Applied Physics
SN - 0021-8979
IS - 4
M1 - 043115
ER -