Basic study of coherent hot electron generation and its application for ultrafast devices

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In this research, the generation and the measurement of the coherent hot electron, the possibility of transport control of the hot electron based on the wave principle and the realization of the nanometer-pitch electron-wave grating were studied.The realization possibility of the electron wave device depend on the coherence of the electron. The coherent length of the quasi-equilibrium electron in the modulation doped structure has been estimated to be quite long at very low temperature and under very low applied voltage. On the other hand, the phase of the non-equilibrium electron or the hot electron is broken by the spontaneous emission of the L0-phonon and its phase braking time is supposed to be as short as 0.2ps. However, for operation at temperature higher than 4K and under appropriate voltage application, it is interesting to consider how to use the hot electron for the electron wave device.We are estimating the coherent properties of the hot electron using the double barrier res … More onant tunneling diode(RTD). When the phase of the electron is broken in the well of the RTD,the width of the resonant level increases. Then by measuring the width of the resonant level of the RTD,we can estimate the phase braking time or the coherent properties of the hot electron in the well. Therefore we have fabricated GaInAs/InP double barrier RTDs by OMVPE.From the second derivatives of the I-V curves, we have measured widths of resonant levels of RTDs. We compared the dependence of the level width on the barrier thickness with theory to estimate the coherent length. The apparent coherent length in GaInAs was 80-120nm at 4K when the energy of the electron was 100meV.Projecting to control the transport of the hot electron by electron wave diffraction in a quantum grating, we are developing nanofabrication technology of ultrafine pitch grating. We have achieved 40nm-pitch InP gratings embedded in GaInAs by combining electron-beam lithography, special wet chemical etching and organometallic vapor phase epitaxy overgrowth. Furthermore, to observe the ultrafine diffraction pattern of the electron wave, we have fabricated 40nm-pitch arrays of ultrafine electrodes by the lift-off technique. To align the embedded grating and the ultrafine electrode, we have developed the electron-beam alignment technique by using Platinum marks. Less