Effects of different insertion layer thicknesses on structural and optical properties of GaN/Al0.5Ga0.5N/GaN coupled multiquantum wells

Abstract

Giant piezoelectric effects on the structural and optical properties of coupled multiquantum wells consisting of GaN (10 Å)/AlGaN (Tib Å)/GaN (20 Å) bounded by Al0.5Ga0.5N (100 Å) barriers have been investigated by high-resolution x-ray diffraction, time-integrated and time-resolved photoluminescence measurements. As a result of these measurements, the optical and structural properties are strongly dependent on the inserting barrier thickness of Tib ∼ 5 Å. By inserting the AlGaN layer of thickness up to 5 Å, the internal piezoelectric field rapidly increases but slowly decreases beyond the critical thickness. And the main emission line of photoluminescence is dramatically redshifted with respect to that of the normal GaN/AlGaN quantum well and is blueshifted with further increasing thickness. The spectral peak position of time-resolved photoluminescence with the inserting layer thickness of 4 Å redshifts as the delay time increases. These experimental results are well explained by the quantum confined Stark effect based on the giant piezoelectric field in strained GaN/AlGaN coupled multiquantum wells.