Optical characterization of digital alloy In0.49Ga0.51P∕In0.49(Ga0.6Al0.4)0.51P multi-quantum-wells grown by molecular beam epitaxy

Abstract

An In0.49Ga0.51P∕In0.49(Ga0.6Al0.4)0.51P multi-quantum-well (MQW) structure grown by molecular beam epitaxy using a digital alloy method was parametrically investigated by photoluminescence (PL) measurement performed in a temperature range of 10–290K. The PL peak energies did not change with increasing temperature up to 60K, while the PL peak energy monotonously decreased with increasing temperature beyond 60K. From the curve fit of the linewidth full width at half maximum of the PL peak, it was observed that the homogeneous broadening of In0.49Ga0.51P∕In0.49(Ga0.6Al0.4)0.51P MQW with digital alloy barriers due to scattering by longitudinal optical phonons was smaller than that of InGaAs∕InGaAlAs MQW with digital alloy barriers. This is in accordance with the existence of a relatively weak phonon-related PL peak in the PL spectrum of InGaAlP digital alloy, as compared with InGaAlAs digital alloy. The fit of the integrated PL intensity shows the occurrence of a nonradiative recombination process with an activation energy E1=24.4meV up to 60K. On the other hand, the process of nonradiative recombination with an activation energy E2=109meV occurred above 60K, which is in good agreement with one-half of the calculated total confinement energy ΔE of the electron-hole pair in the quantum well (∼108meV). The In0.49Ga0.51P∕In0.49(Ga0.6Al0.4)0.51P MQW structure with digital alloy barriers has larger activation energy (E2=109meV) than In0.49Ga0.51P∕In0.49(Ga0.6Al0.4)0.51P MQW (E2=90meV) with analog alloy barriers. Therefore, the thermal emission of carriers into the barrier can be reduced at temperatures above 60K due to the high effective barrier height.

Atomic variations in digital alloy InGaP/InGaAlP multiple quantum wells due to thermal treatment

“…The deterioration of the crystallinity due to the abrupt termination of growth can be overcome by using the digital alloy (DA) method, which is used to form short-period superlattices (SPSLs). [7][8][9][10][11][12] When the InGaP/InGaAlP MQWs are grown using the DA method with a combination of InGaP and InAlP ternary alloys, nonradiative defects, which decrease the device characteristics of the LEDs, are generated in the strained InGaP/ InGaAlP MQWs. 13,14) The device performance of InGaP/ InGaAlP-based LEDs can be improved by thermal annealing to enhance the quality of DA materials.…”