K.S.A. Butcher

Multilayer GaSb/GaAs self-assembled quantum dots grown by metalorganic chemical vapor deposition

Abstract A mutilayer structure of self-assembled GaSb/GaAs quantum dots (QDs) has been grown for the first time by metalorganic chemical vapor deposition (MOCVD) in the Stranski–Krastanow (S–K) growth mode. Evidence of the growth of the self-assembled quantum dots was provided using transmission electron microscopy. This study shows that the GaSb/GaAs heterostructure is well controlled and there is no sign of the intermixing that often occurs for this system. The existence of the quantum dots and of a wetting layer was also supported by photoluminescence spectra. These results open the way to the realization of GaSb/GaAs QD superlattice structures in which the islands have equal size in all layers. The QD structures also provide an opportunity for studying electronic coupling between islands.

Cathodoluminescence of GaSb/GaAs self-assembled quantum dots grown by MOCVD

Cathodoluminesence (CL) studies were performed for GaSb self-assembled quantum dots grown by atmospheric pressure metalorganic chemical vapour deposition on GaAs substrates. The evolution of quantum dot size and density was examined for samples grown for different periods. The CL peaks shifted to higher energies from 0.95 to 1.05 eV as the dot growth time increased from 3 to 7 s. This trend indicates a significant size quantisation effect for partially relaxed structures.

UV Moderation of Nitride Films during Remote Plasma Enhanced Chemical Vapour Deposition

GaN and AlN thin films have been grown by remote plasma enhanced chemical vapour deposition (RPE-CVD) with the assistance of ultraviolet (UV) irradiation during growth. High quality AlN insulating layers have been grown at room temperature for MIS devices. Film resistivities of up to 2.8 × 10 16 Ωcm and breakdown fields of over 1.8 MV/cm have been achieved. Preliminary results for GaN indicate severe nitrogen loss when using UV desorption with an ammonia plasma, however no nitrogen deficit is seen when using a nitrogen plasma. Optical absorption data show substantial improvement in material quality when using a nitrogen plasma in preference to an ammonia plasma for GaN RPE-CVD growth.