Control of defects in bulk indium phosphide crystals: The relationship between growth parameters and the control of crystallographic and electronic properties.

摘要

This research advances basic understanding in the field of indium phosphide (InP) crystal growth and defect control. Control of defects is a paramount concern in InP bulk crystal growth, since the objective is to grow a perfect single crystal. Engineering controls developed in this research effort are: applied magnetic fields, thermal gradient control (active or passive), and crystal shape/diameter control. The subject of this thesis is the exploitation of methods to control the defects during InP crystal growth, and post-growth thermal treatment to optimize the crystal properties.; Experimental crystal growth studies are used to isolate different types of defects so they can be compared under different growth conditions.; The axial field is shown to be a practical technique for growing twin-free InP crystals. An axial field of 2kG suppresses turbulent melt convection, reducing the temperature fluctuations from ±15° to ±1°C, enabling growth of flat-topped (90° growth angle) crystals of twin-free InP with no edge faceting.; Crystals grown under cusped magnetic field conditions can be grown twin-free only if the conical growth angle is near 35°, where edge faceting is observed.; A series of experiments was carried out to correlate twinning defects with specific process controls. The controls tested were the magnetic field configuration, the dopant species, and the conical growth angle. Growth controls, which proved most effective in the suppression of twins are: (1) Axial magnetic field combined with large conical growth angle 80–90°. (2) Cusped magnetic field combined with small conical growth angle, 35°. (3) Axial magnetic field combined with sulfur doping and a small angle, 35°. (4) Cusped field with any other dopant than sulfur and a small angle, 35°.; A controlled seeding technique for InP crystal growth has been demonstrated employing necking to suppress the propagation of dislocations from the seed-melt interface.; This thesis reveals the following effects on intrinsic and extrinsic point defects in semi-insulating InP when high temperature annealing is used after growth. (1) The hydrogenated vacancy complex, VH₄ is completely annihilated after annealing. (2) The ionized iron concentration, Fe2+ is thermally converted to Fe3+ in direct proportion to the VH₄ reduction, under slow cooling conditions. (3) Under rapid cooling conditions, thermal conversion is not complete, because some of the iron is quenched in to nonsubstitutional sites.; This dissertation covers the important technological aspects of bulk InP crystal growth, defect control, and characterization methods; emphasizing the evaluation of materials properties by determining defect concentrations and mapping their uniformity. (Abstract shortened by UMI.)