Highly radiative nature of ultra-thin c-plane Al-rich AlGaN/AlN quantum wells for deep ultraviolet emitters
Abstract
Temperature-dependent photoluminescence (PL) lifetimes were measured for a series of ultra-thin c-plane Al0.61Ga0.39N/AlN multiple quantum wells (QWs) on bulk AlN substrates with the well thickness varying from 0.6 to 2 nm. At temperatures below 75 K, estimates of the internal quantum efficiency indicate that the recombination is primarily radiative, with a lifetime of ∼160 ps for the 0.6 nm QWs, comparable to the low temperature PL lifetime observed in bulk AlGaN films of a similar Al content. This short lifetime is observed despite the presence of layer thickness fluctuations and the quantum-confined Stark effect associated with the large polarization field in the heterostructures, which tend to increase the radiative lifetime. This behavior is explained using many-body calculations of radiative recombination rates that extend beyond the conventional ABC rate equation model by accounting for both excitons and free carriers within a nonequilibrium Green's function formalism. The results indicate that the combination of the large wave function overlap integral (∼0.65) and exciton binding energy (1.82 times the 3D Rydberg) for the 0.6 nm QWs leads to an ∼20-fold increase in the radiative recombination rate relative to that obtained for the 2 nm QWs. This greater radiative recombination rate competes favorably with trapping at interface fluctuations and defect-induced nonradiative recombination that dominates recombination at higher temperatures.
Document Details
- Document Type
- Pub Defense Publication
- Publication Date
- Mar 11, 2019
- Source ID
- 10.1063/1.5087543
Entities
People
- C. R. Haughn
- G. A. Garrett
- G. Rupper
- M. Wraback
- N. M. Johnson
- Thomas Wunderer
- Zhengyu Yang
Organizations
- Defense Advanced Research Projects Agency
- PARC
- United States Army Research Laboratory