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If electrons are transferred across an interface between an area of high and low effective mass, parallel momentum conservation leads to electron refraction effects, which are evident on InAs-AlSb resonant tunneling diodes and also, e.g., in ballistic electron emission microscopy. In ballistic electron emission microscopy on Au-GaAs Schottky diodes, the difference in effective mass is especially large and as a consequence of electron refraction, the spatial and energetic resolution for structures buried below the metal-semiconductor interface are considerably reduced. If a resonant $({\mathrm{G}\mathrm{a}\mathrm{A}\mathrm{s}\ensuremath{-}\mathrm{A}\mathrm{l}}_{x}{\mathrm{Ga}}_{1\ensuremath{-}x}\mathrm{As})$ tunneling structure is grown directly below the sample surface, however, only electrons with zero wave vector parallel to the barriers can be transmitted resonantly. As a consequence, the energetic and spatial resolution is expected to be enhanced for buried structures. Moreover, the underlying principle can be applied to devices in order to fabricate electron injector structures with narrow energy distribution both in ${E}_{\ensuremath{\perp}}$ and ${E}_{\ensuremath{\parallel}}.$

Institut fu ¨r Festkorperelektronik und Mikrostukturzentrum der Technischen Universita¨t Wien, Floragasse 7, A-1040 Wien, Austria~Received 14 August 2000; revised manuscript received 31 January 2001; published 20 April 2001!Double barrier resonant tunneling diodes ~DBRTD’s! buried below an Au/GaAs interface usually lead to alinear increase in the spectra obtained in ballistic electron emission microscopy/spectroscopy experiments. Ifgrown directly below the Au/GaAs interface the spectrum changes to a clear steplike shape, which has beenattributed to lateral wave-vectork