High precision parabolic quantum wells grown using pulsed analog alloy grading technique: Photoluminescence probing and fractional-dimensional space approach

Abstract

The designed GaAs/AlGaAs parabolic quantum well (PQW) was grown using a pulsed analog alloy grading (PAAG) technique with molecular beam epitaxy by setting a significantly lower growth rate, growth time variation with growth rate change, and growth interruptions for stabilization of Al source temperature. The growth conditions allowed to achieve high precision parabolic potential of the PQW due to the arrangement of crystalline lattice by migration of group-III atoms and smoothing of interfaces under As overpressure. The structure was probed by scanning transmission electron microscopy and investigated via excitation power and temperature dependent photoluminescence (PL). The origin of the PL spectra lines was corroborated by fractional-dimensional space approach with dimensionality factor varying from 2.46 for confined to 3 for bulk semiconductor radiative transitions. Up to 5 PQW equidistant subbands in conduction and valence bands are observed by filling the states with photoexcited carriers. The PL of the excited PQW states is resolved up to 240 K temperature. The results indicate excellent agreement between luminescent properties of the designed PQW using numerical Schrödinger equation solver and the produced PQW using PAAG technique. It validates the developed PAAG technique as a powerful tool for PQWs growth to tailor a basis for more sophisticated quantum systems for near-infrared to terahertz emitters employing interband and intersubband transitions.