Nonradiative centers in deep‐UV AlGaN‐based quantum wells revealed by two‐wavelength excited photoluminescence

Abstract

We have succeeded in detecting nonradiative recombination (NRR) centers in InAlGaN multiple quantum wells (MQWs) for the sterilization wavelength at around 265 nm by our scheme of two-wavelength excited photoluminescence (PL). Samples studied are InAlGaN multiple quantum well structures with InAlGaN electron blocking layer grown on sapphire (0001) substrates by metal-organic chemical vapor deposition (MOCVD) technique at the growth temperature of 880 8C (sample A) and 920 8C (sample B). The MQW consists of three InAlGaN wells of 2 nm sandwiched by 7 nm InAlGaN barrier layers. With the addition of the below-gap excitation (BGE) light of 1.17 eV, the PL intensity decreased for the sample A but increased for the sample B. Both change in the PL intensity implies the existence of NRR centers, which were activated by the BGE. We attribute both intensity change to two-levels model and one level model, respectively. Based on rate equation analysis, a set of NRR parameters of sample B was determined by utilizing a saturating tendency of the PL intensity change. Spectroscopic and quantitative advantages of the method enable us to clarify energy distribution of NRR centers without providing electrode.

Photoluminescence Characterization of Nonradiative Recombination Centers in Light Emitting Materials by Utilizing Below-Gap Excitation: A Mini Review of Two-Wavelength Excited Photoluminescence

“…The BGE energy dependence gives us a direct clue for determining the origins and improving the growth condition. An incorporation of small amount In is effective for improving the internal quantum efficiency, but quite sensitive to the growth temperature [25]. These results are to be discussed with previous reports on deep levels in AlGaN as a function of Al composition [33][34][35].…”

“…Therefore any increase or decrease of the PL intensity due to the addition of the BGE implies a sign of NRR centers which can be interpreted by either one level model or two levels model at their simplest form. Measurements of GaAs-based quantum wells (QWs) [11][12][13][14][15][16][17][18][19][20][21], GaN/InGaN-QWs [19][20][21][22][23], AlGaN-QWs for deep UV wavelength region [24][25], GaPN [26][27] and Ba 3 Si 6 O 12 N 2 : Eu 2+ phosphors [28] have been done by such straightforward experimental principle.…”

Structural and optical investigations of AlGaN MQWs grown on a relaxed AlGaN buffer on AlN templates for emission at 280nm

“…Besides threading dislocations (TDs), the impurity (such as oxygen) effect is greater in AlN epitaxial layers than in GaN due to low diffusion length of Al atoms (high sticking coefficient) and increased affinity of Al to oxidize, which cause rather high density of defects in AlGaN layers with Al content larger than 50% [6,7]. Unlike the defects in InGaN/GaN MQWs which have been widely studied (even though the influence of defects on emission efficiency is still controversial) [8][9][10][11][12][13], only a few reports have focused on the study of the typical defects in metal organic vapor phase epitaxy (MOVPE) grown AlGaN MQWs on AlN templates for DUV devices and especially their influences on the optical emission [14][15][16][17].…”

Detection of Nonradiative Recombination Centers in GaPN by Combining Two‐Wavelength Excited Photoluminescence and Time‐Resolved Photoluminescence

“…In previous work, with temperature-dependent properties, we used temperature-controlled metal cryostat for TWEPL measurement. [37,38,40,[50][51][52][53][54] Based on these studies, we prepared a glass cryostat for the TWEPL measurement in which the sample was immersed in liquid nitrogen (N 2 ) directly to avoid surface temperature effect. Two different light sources of AGE, a THG Nd:YAG laser with hν A1 ¼ 3.49 eV (355 nm wavelength) and a semiconductor laser with hν A2 ¼ 2.33 eV (532 nm), were used as CB excitation and IB excitation, respectively.…”