MOVPE Growth and Characterization of Low-Dimensional III-V Semiconductor Structures

Sammanfattning: Metalorganic vapour phase epitaxy is used for growth of low-dimensional III-V semiconductor structures. The roughness of heterointerfaces in GaAs/GaInP quantum well structures is studied by photoluminescence emission from extremely narrow quantum wells. Results obtained for GaAs/GaInP quantum wells are compared to the more thoroughly investigated GaInAs/InP material combination. The potential of using a strain induced transition from a 2-dimensional layer-by-layer growth mode, towards 3-dimensional island growth, for generation of self-assembled quantum dots is demonstrated for the highly strained InP/GaInP and InAs/InP heterocombinations. Self-assembled dots of InP can also be formed on a GaAs substrate for a wide range of growth rates and growth temperatures. Characterization by atomic force microscopy shows that the initial nucleation of self-assembled dots strongly depends on the growth rate and the growth temperature, resulting in a variable surface density of dots, as well as a variable dot size. Growth of modulation doped GaInAs/InP quantum wells at growth conditions previously optimized with respect to narrow line-widths in photoluminescence, results in an extremely high electron mobility, allowing detailed studies of the most prominent low-temperature scattering mechanisms. By etch-and-regrowth of a modulation doped GaInAs/InP quantum well structure, the formation of a quantum point contact is demonstrated. The quantum point contact exhibits a characteristic quantized conductance up to 10 K. After the initial optimization of the growth conditions with respect to photoluminescence properties of narrow GaAs/GaInP quantum wells, electron tunneling in GaAs/GaInP double-barrier resonant tunneling diodes is demonstrated. The active areas of the diodes can be scaled by the insertion of an array of embedded W discs in the upper GaAs cap layer. Vacant positions in the W disc array define the vertical current channel, while the areas without vacancies are semi-insulating due to an overlapping Schottky depletion from the W disc array.