| About this Abstract |
| Meeting |
2011 Electronic Materials Conference
|
| Symposium
|
2011 Electronic Materials Conference
|
| Presentation Title |
M10, Effects of Dislocations on Luminescence in m-Plane InGaN Quantum Wells |
| Author(s) |
Yu Huang, Kewei Sun, Alec Fischer, Qiyuan Wei, Reid Juday, Fernando A Ponce, R. Kato, Toshiya Yokogawa |
| On-Site Speaker (Planned) |
Yu Huang |
| Abstract Scope |
Group III nitride semiconductors thin film for light emitting devices are typically grown on <I>c</I>-plane sapphire substrates, and have encountered important materials challenges, notably polarization fields due to the absence of a center of symmetry in the wurtzite crystal structure. In addition, the strain due to lattice mismatch between InGaN and GaN produces strong piezoelectric fields, which cause the spatial separation of electrons and holes in the active region by the quantum-confined Stark effect (QCSE), leading to lower radiative recombination efficiencies. A preferred approach to reduce or nullify the QCSE is to rotate the crystal growth direction so that the net polarization field lies parallel to the interface plane. This can be accomplished by growing nitride materials on <I>a</I>-plane or <I>m</I>-plane substrates. Such non-polar device structures are expected to have no internal fields in the quantum well (QW) region. It has been observed, but not reported, the appearance of two peaks in the luminescence of InGaN QWs grown on the <I>m</I>-plane configuration. The origin of the double-peak emission is not understood. In this talk, we report on a study of the structural and optical properties indicating that <I>in-plane</I> piezoelectric fields are introduced by lattice mismatch relaxation that breaks the continuity of the quantum wells, resulting in regions where PE fields produce the red-shifted peak. A correlation has been established between the optical and structural properties of blue light-emitting diode structures with an indium composition of about 15% in the active region grown on free-standing <I>m</I>-plane GaN. An inhomogeneous spatial distribution in the InGaN quantum well emission is observed with two distinct peaks at 428 and 462 nm at room temperature, which are associated with the presence of dislocations originating at the InGaN layers. The difference in peak energy positions is consistent with the presence of <I>in-plane</I> piezoelectric fields within the dislocated regions compared to the absence of such fields in the dislocation-free regions. The longer wavelength peak exhibits a continuous blue-shift with increasing injection current, attributed to enhanced screening of the piezoelectric fields. It also exhibits slow recombination rates at low temperatures, attributed to carrier separation by piezoelectric fields along the <I>in-plane</I> polar <I>c</I>-direction in the dislocated regions, an effect that is reduced by carrier thermal activation at higher temperatures. |
| Proceedings Inclusion? |
Undecided |