(Color online) (a) Diagram of the top VB of a c-plane Al x Ga1−x N/ Al y Ga1−y N heterostructure. (b) VB line-up of AlGaN/AlN on the c-plane and nonpolar plane. Possible geometries of LD cavities for (c) c-plane AlGaN/AlN with a low Al content, (d) c-plane AlGaN/AlN with a high Al content, and (e) nonpolar AlGaN/AlN (x′ polarization) where red solid, black solid, and black dashed arrows represent the c-axis, electric-field, and propagation direction of light, respectively.
(Color online) (a) Overlap integral of Al x Ga1−x N/AlN QWs and (b) transition energy and wavelength of Al x Ga1−x N/AlN QWs, (c) overlap integral of GaN/Al y Ga1−y N QWs, and (d) transition energy and wavelength of GaN/Al y Ga1−y N QWs. Crystal orientation is the c-plane. In experiments, well width becomes integral multiple of monolayer thickness of well material.
(Color online) Well width dependence of the threshold carrier density of c-plane GaN/AlN QWs. (a) Threshold dependence on QCSE and (b) threshold dependence on Al content.
(Color online) VB energy structure of (a) nonpolar GaN/Al y Ga1−y N and (b) nonpolar Al x Ga1−x N/AlN strained bulks. Origin of VB energy is set to the VB energy of an unstrained bulk crystal without crystal-field splitting and spin-orbit interaction. Inset in (a) magnifies the VB structure with an Al content from 0.0 to 0.3.
(Color online) (a) Overlap integral of GaN/Al y Ga1−y N QWs, (b) transition energy of GaN/Al y Ga1−y N QWs, (c) overlap integral of Al x Ga1−x N/AlN QWs, and (d) transition energy of Al x Ga1−x N/AlN QWs. Crystal orientation is the nonpolar plane.
(Color online) Optical gain of 1-nm-thick AlGaN QWs on the (a) nonpolar plane and (b) c-plane.
(Color online) Comparison of threshold carrier density between nonpolar and c-plane GaN/AlN QWs with well widths of 1 nm.
(Color online) Threshold carrier density of 1-nm-thick Al x Ga1−x N/Al y Ga1−y N QWs. Black, red, and blue lines represent the threshold for c-plane QWs, nonpolar QWs with (x′-polarization), and nonpolar QWs with (y′-polarization), respectively. Small numbers indicate Al content.
In-plane effective masses of c-plane QWs.
In-plane effective masses of nonpolar plane QWs.
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