Novel Insulated Gate Structure having Ultrathin Si Quantum Well for Realization of InP-Based Ultra High-Frequency and High-Power Devices

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The purpose of this study is to provide a breakthrough for realization of InP-based ultra high-frequency and high-speed devices using a novel insulated gate structure having a "ultrathin Si quantum well". The main results obtained are listed below:l ) Novel in-situ characterization methods for semiconductor free surfaces as well as MIS interfaces during the interface formation process were established based on a UHV-based contactless C-V method and a photoluminescence surface state spectroscopy (PLSィイD13ィエD1).2) By combining these methods with a UHV-STM/STS and a XPS analyses, the pinning center was found not to be a point with discrete deep level, but to be an area with gap state continuum. This seems to support the unified disorder induced gap state (DIGS) model for Fermi level pinning proposed by our group, which is the basis of the concept of present "insulated-gate structure having ultrathin Si quantum well".3) The insulated-gate structure having ultrathin Si quantum well with precisely controlled quantum well thickness was successfully realized by MBE growth of ultrathin psedomorphic Si layer on the InP-based materials and subsequent thinning of the Si layer by ECR plasma-induced partial nitridation.4) Under the optimum ECR nitridation condition, this process realized the InP MIS structure with extremely low interface state density of 2x10ィイD110ィエD1cmィイD1-2ィエD1eVィイD1-1ィエD1. This value is the best of all the oxide-free InP MIS structures reported so far.5) An InP MISFETs fabricated using the present insulated gate structure having the ultrathin Si quantum well exhibited excellent gate control capability, high effective electron mobility and stable operation. The drift of the drain current was found to be as small as 1.9% after 10ィイD14ィエD1 s operation.