Growth and characterization of InAs microclusters in InP and InAsP/InP heterostructures by low pressure MOCVD using tertiarybutylarsine

Abstract

InAs microclusters embedded in an InP matrix and InAs x P 1– x /InP (0.1 ≤ x≤0.3) strained multiple quantum wells (SMQW) have been prepared by LP-MOCVD using tertiarybutylarsine (TBAs) as a substitute for AsH 3. The relatively large cracking efficiency of TBAs resulted in low As/In ratios (from 4.3 to 8.8) for InAs/InP structures and low As/P ratios (from 1×10 -3 to 3.5×10 -3 for InAs x P 1– x /InP (0.1 ≤ x ≤0.3). High-resolution X-ray diffraction (HRXRD) and photoluminescence (PL) show that the TBAs-grown material is of high quality. The HRXRD patterns of InAs microclusters embedded in the InP matrix demonstrate that the InAs unit cell is tetragonally distorted in accordance with the elasticity theory. For InAs microclusters embedded in the InP matrix, the 7 K emission PL peak shifts from 1.35 to 1.39 eV when the InAs coverage is reduced from 0.8 to 0.2 monolayers, a clear indication of a lateral size effect. Picosecond time resolved PL shows a weak coupling of excitons confined by these InAs microclusters. We report also the results of a study of the interface roughness of InAs x P 1– x /InP heterostructures. HRXRD, PL, absorption and photoconductivity (PC) measurements for InAsP/InP SMQW reveal that the InAsP/InP interface is very sensitive to growth procedure. For nonoptimal growth procedures a large density of interface states is created, probably as a consequence of compositional modifications within the interface region. The optical measurements clearly resolve the fundamental intersubband transitions in the InAsP/InP SMQW, including heavy hole-light splittings, even at room temperature.