MOCVD Nucleation And Growth Of Antimonide Based Compound Semiconductors

Nowadays, the research on antimonide semiconductors has made greatprogresses, such as the applications in monolithic microwave integrated circuit(MMIC), infrared lasers, infrared focal plane array detectors, quantum cascadelasers, quantum well laser, quantum dot laser, thermoelectric devices,thermophotovoltaic devices and resonant tunneling diodes.Band alignment between different antimonides (or antimonide and many otherIII-V semiconductors) could be a type-II band alignment. The spatial separation ofelectrons and holes in type-II structures results in long exciton lifetimes. Therefore,the heterostructures made up of antimonides are very promising for optoelectronicsapplications.However, the far-ranging practical applications of antimonide thin film inreliable functional devices have been delayed by the difficulties in acquiringhigh-quality epitaxial layers. Main problem in the growth of antimonide epitaxiallayers on other main semiconductor substrates is the relatively large lattice mismatch(~8%of GaSb/GaAs) that leads to a high threading dislocation density. In addition,being different from other group III-V semiconductors, antimonide such as GaSbcomprises two metallic elements exclusively. The metallicity of Sb results in a lowsurface mobility of adatoms, which usually makes the surface of GaSb epitaxiallayer rough. There is indeed a need for systematically investigating on the MOCVDgrowth of antimonides which lags far behind MBE growth.In this paper, the initial growth stage of GaSb on GaAs (001) by low pressureMOCVD (LP-MOCVD) has been investigated. The dependence of the nucleation ongrowth temperature, growth pressure and vapor V III ratio was studied. Thenucleation characters include the islands density, size and size uniformitydistribution. The nucleation mechanism was discussed by the effect of growth temperature, growth pressure and vapor V III ratio on the density, size and sizeuniformity of GaSb islands. With the growth temperature increasing from500to610℃and the growth pressure increasing from50to1000mbar, the islands densityincreases at first and then decreases. But with the V/III increasing from0.5to3, thetrend is contrary.Then, one group orthogonal experiments of GaSb films growth on GaAssubstrates has been designed, and the crystallinity and microstructure characteristicsof the films have been comparatively analyzed to achieve the optimum growthparameters.It was demonstrated that the optimized GaSb thin film has a low fullwidth at half maximum (358arc sec) of the (004) ω-rocking curve, and a smoothsurface with a low root-mean-square roughness of about6nm, which is typical inthe case of the heteroepitaxial single-crystal films. In addition, we studied the effectsof layer thickness of GaSb thin film on the density of dislocations by the Ramanspectra.At last the growth of InSb/GaSb quantum dots has been investigated. Thedependence of InSb/GaSb quantum dots properties on many growth parameters wasdiscussed. A better sample with a high InSb/GaSb quantum dots density of1.691010cm-2was obtained.