Open AccessOptical light polarization and light extraction efficiency of AlGaN-based LEDs emitting between 264 and 220 nm
Author(s) -
Martin Guttmann,
Frank Mehnke,
Bettina Belde,
Fynn Wolf,
Christoph Reich,
Luca Sulmoni,
Tim Wernicke,
Michael Kneissl
Publication year - 2019
Publication title -
japanese journal of applied physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.487
H-Index - 129
eISSN - 1347-4065
pISSN - 0021-4922
DOI - 10.7567/1347-4065/ab0d09
Subject(s) - light emitting diode , quantum efficiency , electroluminescence , optoelectronics , materials science , diode , photoluminescence , wavelength , mole fraction , polarization (electrochemistry) , optics , chemistry , physics , layer (electronics) , composite material
The influence of aluminum mole fraction of Al x Ga 1- x N/Al y Ga 1- y N multiple quantum wells (MQWs) on the optical polarization, light extraction efficiency (LEE) and external quantum efficiency (EQE) of deep ultra violet light emitting diodes in the wavelength range between 264 and 220 nm is investigated. The on-wafer EQE decreases from 0.6% to 0.00013% in this wavelength range. Polarization resolved photoluminescence and electroluminescence measurements show a change from dominant transverse-electric to dominant transverse-magnetic polarized light emission with increasing aluminum mole fraction in the MQW. The quantitative agreement with k · p calculations allow to ascribe this shift to a change of the characteristic of the Γ 7+ valance band. Ray tracing simulations predict a reduction of the on-wafer LEE from 4% to 1.5%. Therefore the dramatic drop of the EQE in this wavelength range cannot be attributed to a drop in LEE and is most likely dominated by charge carrier injection and radiative recombination efficiency.