Material Gain Engineering in Staggered Polar AlGaN/AlN Quantum Wells Dedicated for Deep UV Lasers

Abstract

Material gain is calculated for polar staggered Al x Ga 1-x N/AlN quantum wells (QWs) of various architectures: i) with a step-like Al y Ga 1-y N barrier grown prior the Al x Ga 1-x N QW, ii) with a step-like barrier grown on the QW, and iii) with a step-like barrier grown prior and on the QW. The obtained results are compared with those obtained for reference Al x Ga 1-x N/AlN QWs. With the increase in Al concentration in the reference QW the gain peak blueshifts and its strength decreases mainly due to the Al-related increase in the electron effective mass. The step-like barrier is able to tune the spectral position of the gain peak and enhance the gain strength. For the staggered QWs with step-like barriers grown prior to the QW a blueshift of the gain peak is observed while a redshift of the gain peak is observed for QWs with the step-like barrier grown on the QW. It is shown that a strong material gain in the 260-280 nm spectral range can be achieved with the staggered Al x Ga 1-x N/AlN QW with x = 30% and 1 nm thick step-like Al y Ga1-yN barrier of high Al concentration (y = 0.7-0.9). The increase in Al concentration in the staggered QWs shifts the gain peak to deeper UV but the strength of material gain decreases.

Material Gain in Polar GaInN and AlGaN Quantum Wells: How to Overcome the ‘Dead’ Width for Light Emitters in These QW Systems?

“…In the context of studies reported in this work, the engineering of QW width in broad range can be also very interesting for staggered polar GaInN/GaN and AlGaN/AlN QWs. So far, large widths were not considered for staggered QWs as a drastic decrease in gain with increasing QW width was observed [59]. Since this polar QW system is non-intuitive, considering large widths in staggered QWs can lead to unexpected results, as shown in this paper for rectangular QWs.…”

“…Figure 5 shows spectra of the TM mode of the material gain calculated for Al0.8Ga0.2N/AlN QWs of different widths at the carrier concentrations of 2.5 and 3.0×10 19 cm -3 . In contrast to the Ga0.8In0.2N/GaN QW, the fundamental transition in this QW is with TM polarization [59] and therefore the TM mode of the material gain is plotted in this figure. The change in the spectral position and the intensity of gain peak is very similar to that observed for Ga0.8In0.2N/GaN QW.…”

“…Therefore, it is a very interesting issue to carefully study material gain for GaInN and AlGaN over a wide range of widths. So far, gain calculations have been reported for GaInN and AlGaN QWs in several articles [45,[52][53][54][55][56][57][58][59], but for wide QWs such calculations have not been reported in these articles. The widest QWs, for which optical gain calculations have been reported so far, are the 9 nm AlGaN wells [60].…”

Theoretical and Experimental Studies on Material Gain for Wide Polar InGaN Quantum Well‐Mechanism Leading to Electric Field Screening and Lasing

“…Quite often, staggered QWs have been considered. [18][19][20][21][22][23][24] In this case, it is possible to obtain a better ground-state electron-hole overlap with appropriate polarization engineering, but the total thickness of the step-like barriers and QW is still below 5 nm, [18][19][20][21] which is very far from the width typical of non-polar QWs in III-V semiconductors, that is, 8-15 nm. [25][26][27][28] In contrast, lasing for wide InGaN QWs has been demonstrated experimentally.…”

Design and Simulation of InGaN-Based Red Vertical-Cavity Surface-Emitting Lasers

“…Interestingly, the staggered MQW structure design has recently been demonstrated in InGaN-based blue LEDs [ 45 ], green LEDs [ 46 ], and AlGaN-based deep UV lasers [ 47 ]. Additionally, the optoelectronic characteristics of InGaN-based green micro-resonant cavity light-emitting diodes (µ-RCLEDs), which consist of a three-layer staggered InGaN MQWs, bottom nanoporous n-GaN DBRs, and top Ta 2 O 5 /SiO 2 DBRs, have been numerically investigated [ 48 ].…”