Non-Equilibrium InSb/InAISb Diodes Grown by MBE
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ABSTRACT The application of non-equilibrium transport techniques to Molecular Beam Epitaxy (MBE) grown InSb/InAlSb heterostructure diodes has produced practical devices such as midinfrared LED's and negative luminescent sources that operate at room temperature. By extending the epitaxial growth to vicinal InSb substrates it has been demonstrated that the temperature window for high quality epitaxy can be lowered by -12 0 C, giving greatly improved epilayer morphology. The degree of misorientation needed for given growth temperatures is shown from Atomic Force Microscope (AFM) measurements to be only -2'. In addition, the lower growth temperature gives improved dopant activation, lower trap densities and lower reverse bias leakage currents, with consequent benefits to device performance.
INTRODUCTION Indium Antimonide (InSb) has the narrowest forbidden energy gap of the binary III-V semiconductors with a cut-off wavelength corresponding to 7pm at room temperature and 5.5 prm at 77K. It has therefore traditionally found uses in infrared photon detection. More recently, InSb has attracted a lot of attention due to its unique material properties which are a result of its narrow energy gap. A low electron effective mass and very high saturation velocity offer the opportunity of very high speed, low power and low noise electronic devices and its narrow bandgap offers the possibility of emitters in the mid infrared waveband that have applications in such areas as gas sensing and spectroscopy. However, the large intrinsic carrier density generated by thermal excitation of electrons into the conduction band has, until recently, limited practical devices to being operated at 77K. Recently, we have reported on growth and fabrication of InSb/In1 ,AlxSb heterostructure diodes that make use of a barrier in the conduction band of the structure to allow extraction and exclusion of the intrinsic carriers in the active region of the device to allow room temperature operation [1]. We have used similar structures operated in forward bias to demonstrate infrared LEDs which show emission with a peak spectral output at -5.8jim [2]. Operated in reverse bias, such structures act as negative luminescent devices, which contravene Kirchhoff's Law because they will absorb radiation without emitting it [3] and have important applications in gas sensing, radiometric reference sources and dynamic infrared scene projectors. We have also reported the first InSb diode lasers with emission wavelengths of 5.1 prm and pulsed operation up to 90K [4].
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Mat. Res. Soc. Symp. Proc. Vol. 484 ©1998 Materials Research Society
Although there are several reports of MBE growth of InSb on (100) surfaces in the literature [5-7], complete optimisation of all the growth conditions remains to be demonstrated. Conditions necessary for Reflection High Energy Electron Diffraction (RHEED) oscillations [8] and maps of surface reconstructions versus substrate temperature and surface stoichiometry [5,6] have also been reported. There have been several studies of dopi
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