This article reviews the pioneering investigations of the luminescence and photoelectric phenomena in type II heterojunctions based on the GalnAsSb/GaSb system. This system is remarkable because it Is possible to create and study heterojunctions with both staggered and broken-gap alignment, the existence of adjacent dual quantum wells for electrons and holes on both sides of the interface. Simultaneous confinement of electrons and holes in these wells causes unique optical and electrical properties of such heterojunctions and greatly modifies the characteristics of optoelectronic devices. The review considers the photo-and electroluminescence spectra of GalnAsSb/GaSb heterojunctions w/!h s!iggered hind i!ignment. The impoCznce o! !unne!!ing-zssisted trzsi!ions through the interface in the radiative recombination of confined carriers is shown. The influence of these transitions on the structure and polarization characteristics of the luminescence spectra is considered. A new mechanism of photocurrent gain in isotype n-N heterojunctions due to hole confinement at the type II interface is discussed. Unusual asymmetric electrical properties of type II heterojunctions with broken-gap band alignment are demonstrated and discussed in connection with their energy band diagrams. Novel IR light sources and photodetectors for the 1.64.7 p m spectral range based on the GalnAsSb/GaSb system are briefly reviewed.

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This review deals with a study of optical and magnetotransport phenomena at a type II arsenide-antimonide heterojunction with a broken-gap alignment. A fundamental feature of this structure is partial overlapping of the InAs conduction band with the GaSb-rich solid solution valence band. In such a heterostructure, electrons and holes are spatially separated and localized in self-consistent quantum wells formed on both sides of the heterointerface. This leads to unusual tunnelling-assisted radiative recombination transitions and novel transport properties. Results of a pioneering study of interface-related luminescence in type II broken-gap GaInAsSb/InAs heterostructures, with a high quality abrupt heteroboundary, grown by the LPE method, are presented. The energy band diagram of the type II broken-gap GaInAsSb/InAs(GaSb) heterostructures and band overlapping control, depending on a doping level and epilayer composition of quaternary solid solution, are discussed. A 2D-electron channel with high Hall mobility at the p-GaInAsSb/p-InAs interface was found and examined. A great deal of attention is paid to quantum transport properties of the semimetal channel in a wide magnetic field range (up to 18 T) at low temperatures. A cyclotron resonance study was used to obtain data on the energy spectrum at the interface and to estimate effective masses for subbands in the semimetal channel. The intriguing behaviour of the 2D-electron system in the presence of localized holes in high magnetic fields and the first observation of integer quantum Hall effect plateaus on the type II single GaInAsSb/InAs heterointerface formed by LPE are demonstrated. A tunnelling-injection laser with high asymmetric band offset confinements based on the type II broken-gap heterojunction is considered. Applications of the interface-induced phenomena in luminescent and transport properties for the design of novel mid-IR optoelectronic devices and Hall sensors are briefly reviewed.

A calculation method of the exponential dependence of the high-energy distribution function in an electric field E is proposed for polar semiconductors. It is shown that in many-valley semiconductors with complicated conduction band structure a strong anisotropy of the electron impact ionization coefficient a(E) will be obtained. I n the case of E 11 (100) or E I I (110) a ballistic transport in the r-valley can occur and the dependence of In a vs.(E,,/E) holds. If E I I (111) the ballistic transport in the I'-valley is impossible and the high-energy distribution function is always formed due to electron scattering from X-valleys. Then the dependence of In a vs.(Eo,/E)2 will be realized for a wide range of fields. The characteristic fields E,, and E,, are connected with the intervalley coupling constants for r-X and X-X scattering, respectively. Impact ionization processes are considered in detail for InSb, GaAs, and InP. The results are compared with accessible experimental data.npennomeH MeTon pacseTa ~~c n o~e~q~i a n b~o t ~~B U C H M O C T H @ Y H I E~E I I I pacnpeaeneHMcI

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