Engineering and investigating the control of semiconductor surfaces and interfaces

The ability to manipulate the electronic properties of semiconductor surfaces and interfaces is of significant technological importance. Band engineering relies on a fundamental understanding of the physics involved in manipulating charge transfer across junctions, at free surfaces, Schottky contacts or heterojunctions. In this paper, the development of new techniques to control and manipulate free surfaces and interface barriers related to the improvement of semiconductor quantum well laser operation are considered. In particular, surface passivation of atomic scale defects on the laser facet using ultra-thin Si layers deposited at 280 deg. C is discussed. The local passivation mechanism was observed directly using a combination of surface science techniques, mainly scanning tunnelling microscopy/spectroscopy (STM/S). Si was found to selectively bond to defects and return the corresponding electronic properties back to the flat band condition. Secondly, heterojunction modification to enhance carrier confinement within the active region of the device is considered using multi-quantum barriers based on theoretical modelling and experimental verification. Limitations of the techniques are also addressed. The use of STM and STS to investigate interface modification on the nanometre scale is highlighted as being relevant to future device fabrication and optimization based on nano-technology. (author)