Effect of Inhomogeneous Broadening in Ultraviolet III-Nitride Light-Emitting Diodes

Abstract

In the past years, light-emitting diodes (LED) made of GaN and its related ternary compounds with indium and aluminium have become an enabling technology in all areas of lighting. Visible LEDs have yet matured, but research on deep ultraviolet (UV) LEDs is still in progress. The polarisation in the anisotropic wurtzite lattice and the low free hole density in p-doped III-nitride compounds with high aluminium content make the design for high efficiency a critical step. The growth kinetics of the rather thin active quantum wells in III-nitride LEDs makes them prone to inhomogeneous broadening (IHB). Physical modelling of the active region of III-nitride LEDs supports the optimisation by revealing the opaque active region physics. In this work, we analyse the impact of the IHB on the luminescence and carrier transport III-nitride LEDs with multi-quantum well (MQW) active regions by numerical simulations comparing them to experimental results. The IHB is modelled with a statistical model that enables efficient and deterministic simulations. We analyse how the lumped electronic characteristics including the quantum efficiency and the diode ideality factor are related to the IHB and discuss how they can be used in the optimisation process.

Optical Gain in AlGaN Quantum Wells: Impact of Higher Energy States

“…Random alloy fluctuations lead to both hole localization effects and bandgap fluctuations [27]. Neglecting the former, we can consider the variation in the bandgap through a normal distribution of band energies [28], which in turn leads to inhomogeneous broadening (IHB) of the gain spectrum. We approximate the spectral IHB through Gaussian convolution with parameter σ IHB .…”

Polarization induced doping for carrier transport in graded III-nitride layers: a simulation study

“…With this addition, excellent agreement at higher currents can be achieved. The simulation parameters have been taken from [11], with an activation model for the acceptors.…”

Carrier Transport in a Deep Ultraviolet Mixed Quantum Well Light Emitting Diode

“…The IHB has been connected with an S-shaped curve of the photon energy versus temperature in photoluminescence experiments and a residual emission bandwidth at cryogenic temperatures [9], [10]. The modification of the phase space filling caused by the IHB affects the carrier transport [11]. This effect cannot be neglected in DUV AlGaN LEDs where the IHB is often much larger than k B T .…”