New Optoelectronic Technique for Characterization of Semiconductors

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9307419 Zhang The objective of this research plan is to develop a new optoelectronic technique for the characterization of semiconductors. The new technique offers coherent measurement of the electronic properties of surfaces and interfaces, as well as carrier dynamics (both phase and amplitude). The technique consists of using a femtosecond laser to illuminate semiconductors, and measuring the electromagnetic radiation produced by the rapid current transients due to optical injection of free carriers into static electric and magnetic fields in the semiconductors. By measuring the time domain waveform of the radiated electric field, the strength and direction of the static electric field can be determined with a non contact approach. A direct application is studying the formation dynamics of the static fields of semiconductor surfaces and interfaces on as grown samples. The influence of the interface fields (both field direction and strength) on the semiconductor can be monitored directly. During monolayer epitaxial growth, surface electrochemical passivation, ultrathin metallic layer deposition, as well as when the sample goes from the liquid helium temperature to its melting temperature. Phenomena such as virtual carrier population associated with the interface field and carrier transport (picosecond quantum Hall effect) at high magnetic fields will be elaborated upon. ***