Polarization engineering of c‐plane InGaN quantum wells by pulsed‐flow growth of AlInGaN barriers

Abstract

Polarization‐field reduction in c‐plane InGaN multi‐quantum well (MQW) structures is achieved by pulsed‐flow growth of quaternary AlInGaN barriers using metalorganic vapor phase epitaxy (MOVPE). The pulsed‐flow growth allows for precise control of the quaternary composition at very low growth rate. In photoluminescence (PL) experiments a blue‐shift of the MQW emission wavelength is observed by successive adjustment of the AlInGaN barriers toward reduced polarization mismatch to the InGaN quantum wells. Accordingly, we find a decreasing radiative lifetime by time resolved cathodoluminescence (TRCL). The application of AlInGaN as barrier material instead of conventional GaN is limited by plastic relaxation. While for InGaN‐QWs emitting in the violet‐blue spectral region, fully polarization‐matched AlInGaN barriers can be realized, for long‐wavelength (green spectral region) severe lattice relaxation is observed leading to inferior optical properties as compared to binary GaN barriers.

Demonstration of Weak Polarization Electric Field III‐N LEDs based on Polar Plane

“…According to previous reported calculation results, the InAlGaN with higher In content and lower Al content can better match with the polarization intensity of InGaN. [ 6 ] Therefore, we prepared two kinds of InGaN/SLs MQWs, marked A2 and A3, by using the structures of SL2 and SL3, respectively, to obtain weaker PEF. The epitaxy structures of InGaN/SLs MQWs are shown in Figure a.…”

“…In order to solve the problems caused by PEF, a variety of approaches have been proposed, such as fabricating LED devices on nonpolar or semipolar GaN, [ 3 ] reducing the width of well or barrier, [ 4 ] adopting trapezoidal wells, [ 5 ] forming polarization‐matched MQWs by quaternary InAlGaN, [ 6 ] etc. Among them, fabricating LED devices on semipolar or nonpolar GaN is the most effective method to address QCSE problem, as the semipolar and nonpolar GaN can reduce or even eliminate PEF without any additional interlayer.…”

“…The QCSE can lead to a spatial separation of electron and hole wavefunction, further reducing the recombination probability and producing a red-shift of emission wavelength, which are unfavorable to the application of III-N LEDs, especially in some emerging fields, such as micro-LED displays and visible light communication. [2] In order to solve the problems caused by PEF, a variety of approaches have been proposed, such as fabricating LED devices on nonpolar or semipolar GaN, [3] reducing the width of well or barrier, [4] adopting trapezoidal wells, [5] forming polarization-matched MQWs by quaternary InAlGaN, [6] etc. Among them, fabricating LED devices on semipolar or nonpolar GaN is the most effective method to address QCSE problem, as the semipolar and nonpolar GaN can reduce or even eliminate PEF without any additional interlayer.…”

Working Mechanisms of Nanoscale Light-Emitting Diodes Operating in Non-Electrical Contact and Non-Carrier Injection Mode: Modeling and Simulation

“…The EL spectra at different frequencies are calculated, as shown in Figure 3 e. When the frequency increased from 5 MHz to 500 MHz, there is a blue-shift in the EL spectrum, which is consistent with experimental results. The blue-shift phenomenon is caused by the quantum-confined Stark effect [ 32 , 33 ]. It is well known that the polarized electric field formed by the polarized charges tilts the energy band of the MQWs; thus, when the number of electrons injected into MQW is relatively small, the emission wavelength is longer.…”

Effect of AlGaN interlayer on the GaN/InGaN/GaN/AlGaN multi-quantum wells structural properties toward red light emission

“…[18][19][20] In order to verify if in plane local relaxation is present in our samples, a direct measurement around the (101 ̅ 0) GaN diffraction peak has been also performed. 21 The surface morphology of all the samples was investigated by Atomic Force Microscopy…”