“Blue” temperature-induced shift and band-tail emission in InGaN-based light sources

Abstract

Electro- and photoluminescence spectra of high-brightness light-emitting AlGaN/InGaN/GaN single-quantum-well structures are studied over a broad range of temperatures and pumping levels. Blue shift of the spectral peak position was observed along with an increase of temperature and current. An involvement of band-tail states in the radiative recombination was considered, and a quantitative description of the blue temperature-induced shift was proposed assuming a Gaussian shape of the band tail.

Exciton localization in semipolar (112¯2) InGaN multiple quantum wells

“…280 K. This can be explained via the hopping processes of excitons through the localized states. 2,3,[15][16][17][18]21 When temperature increases from 10 K to T R!BL , weakly localized carriers are thermally activated and they hop towards other strongly localized states resulting in the initial red-shift of emission energy. With increasing temperature from T R!BL to T BL!R , localized carriers at lower energy levels will be strongly thermally activated to higher levels leading to the blue-shift of emission energy.…”

“…16,17 It should be noted that the ELOC intrinsically exists in InGaN alloys, irrespective of growth orientation employed. 2,3,11,[13][14][15][18][19][20][21] Zhang et al 14 have reported that (11 22) QWs exhibit larger localization depths than polar QWs (estimated from TR-PL measurements at 7 K). Recently, by temperature-dependent photoluminescence (TD-PL) measurements, a strong ELOC degree has been found in (11 22) In 0.2 Ga 0.8 N QWs that causes a blue-shift of the QW exciton emission with rising temperature from $200 K to 340 K, irrespective of excitation source used.…”

“…This will lead to a reduction of non-radiative recombination rates (despite the growth of QWs on high-TDD GaN templates) resulting in an enhanced luminescence efficiency as observed for polar QWs. 2,15 The ELOC will cause a change in the carrier dynamics with increasing temperature resulting in an anomalous emission behaviour, namely, the S-shaped ("red-blue-red" shift) temperature dependence of QW emission energy that is usually attributed to hopping of excitons through the localized states. 16,17 It should be noted that the ELOC intrinsically exists in InGaN alloys, irrespective of growth orientation employed.…”

“…Apart from the polarization fields, another effect that can affect the recombination lifetimes is the exciton localization (ELOC). 2,3,15 The ELOC is derived from self-organized In-rich InGaN regions that can prevent carriers from reaching defects. This will lead to a reduction of non-radiative recombination rates (despite the growth of QWs on high-TDD GaN templates) resulting in an enhanced luminescence efficiency as observed for polar QWs.…”

Excitonic field screening and bleaching in InGaN/GaN multiple quantum wells

“…To date, several groups have discussed the blue shift of the photoluminescence (PL) peak energy in InGaN/GaN heterostructures with increasing carrier injection. The observed carrier dynamics has been described using models that attribute the behavior to either the reduction of the quantum-confined Stark effect due to in-well field screening [5,9,10] band-filling of the energy band tail states [11,12] or both [13,14]. The main reason that these studies have not been able to directly elucidate these complicated dynamics is because traditional time integrated PL and time-resolved PL measurements allow only the radiative recombination dynamics to be directly characterized.…”