Ultrafast valence intersubband hole relaxation in InGaN multiple-quantum-well laser diodes

Abstract

Thermal lensing effect in ridge structure InGaN multiple quantum well laser diodes Envelope-function analysis of wurtzite InGaN/GaN quantum well light emitting diodesThe ultrafast carrier dynamics in InGaN multiple-quantum-well ͑MQW͒ laser diodes were investigated using a time-resolved bias-lead monitoring technique. From the optical selection rules of TE and TM polarized light, one can selectively excite and probe different valence-subband-to-conduction-subband transitions in the MQW structure with different polarized pump and probe light. The subband structure of the MQW structure of the laser diode was calculated and is verified by electroluminescence measurement. Using this technique, ultrafast valence intersubband hole relaxation processes ͑Ͻ0.35 ps͒ were found to dominate the observed carrier dynamics.

Real‐Space Visualization of Energy Loss and Carrier Diffusion in a Semiconductor Nanowire Array Using 4D Electron Microscopy

“…The ultrafast dynamics of charge carriers on materials surfaces play a pivotal role in controlling the applicability of nanoscale materials, especially for one‐dimensional (1D) nanostructures, e.g., nanowires (NWs)/nanorods, which have been extensively used for electronic, optoelectronic, and photoelectrochemical applications due to their interesting and unique properties . For instance, an understanding of nonradiative energy losses at the surface, via carrier–carrier and carrier–phonon interactions, following pulsed‐laser excitation is crucial for wide bandgap semiconductors, e.g., group‐III nitride materials and alloys . Of particular interest is indium gallium nitride (InGaN), which has found wide‐spread use as the active media in solid‐state light‐emitting diodes, laser diodes, and photovoltaic devices because of its tunable bandgap from 0.7–3.4 eV and other characteristics such as direct bandgap, high absorption coefficient, and irradiation resistance .…”

Length dependence of polarization in spontaneous edge emissions from InGaN/AlGaN MQWs laser diodes

“…In the quantum well structure, the valence band splits into sub-bands. The optical selection rules are modified by valence band mixing effect [11]. The optical emission involving electrons from the conduction band and the holes in the most top valence sub-band, is therefore polarized along the direction of vector E of electrical field, and perpendicular to the growth direction axis c in InGaN/AlGaN MQWs.…”

On optical polarization and charge carrier statistics of nonpolar InGaN quantum wells

“…Here, we discuss the system in the steady state case, which applies for continuous optical or electrical excitation. Intrasubband and intersubband relaxation by electron–phonon and electron–electron scattering is much faster ( ()) than interband relaxation by radiative or nonradiative recombination. Thermodynamic equilibrium is therefore established independently both in the CB and VB, with quasi‐Fermi‐levels and for CB and VB, respectively.…”

“…However, this is not caused by different Shockley–Read–Hall, radiative, or Auger coefficients of the two transitions, as the transitions are not independent. This is a consequence of the fast phonon‐assisted interaction ( ()) between the valence subbands, which is by two orders of magnitude faster than the life time of the states (). This results in one quasi‐Fermi‐level for both subbands.…”