Ternary III-V Research Articles

Coherent-potential-approximation calculation of the valence bands of the quaternary alloyInxGa1−xAsyP1−y

The empirical bond-orbital model and the coherent-potential approximation (CPA) are used to study the valence-band structures of the quaternary alloy ${\mathrm{In}}_{x}{\mathrm{Ga}}_{1\ensuremath{-}x}{\mathrm{As}}_{y}{\mathrm{P}}_{1\ensuremath{-}y}$ in a manner similar to our previous work on the ternary III-V compound alloys. The densities of states and the self-energies are correlated with the bond-energy levels and their fluctuations. The concentration variation of the valence-band edge (at ${\ensuremath{\Gamma}}_{15}$) obtained in CPA for the quaternaries matched to the lattice parameters of GaAs and InP are compared with the results from the virtual-crystal approximation. The valence band is shown to contribute significantly to the bowing of the band-gap energy of these alloys.

Alloy scattering in ternary III-V compounds

It is pointed out that the disorder potential utilized to calculate alloy scattering in a pseudobinary semiconductor solid solution can be determined from the heteropolar energy associated with the dielectric method of calculating band structure.

Alloy scattering in ternary III-V compounds

The mean time between scattering due to a random alloy potential is considered. The development makes use of the Warren-Cowley order parameters and uses a pseudobinary alloy model for describing the arrangement of alloy concentrations on the allowed lattice sites. The resulting mean time between scattering is found to depend inversely on the square root of temperature and energy.

Theoretical calculations of electron mobility in ternary III-V compounds

Theoretical calculations have been made of the electron mobility in several ternary III-V semiconductor systems. The scattering mechanisms included in the analysis are polar-optical-phonon scattering, piezoelectric scattering, alloy scattering, and ionized-impurity scattering. Models are also presented and discussed for the variations of material parameters with alloy composition which are needed in the mobility calculations.

Applications of ternary III-V compounds to high-speed microwave modulation

High-speed microwave modulation is obtained by exploiting the intervalley electron transfer time in certain ternary III-V compounds. Saturation of the net carrier drift velocity due to intervalley electron transfer at threshold fields below 3 kV/cm is reported in GaA <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1-x</inf> P <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</inf> and Al <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</inf> Ga <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1-x</inf> As for x = 0.315 ± 0.01 and 0.38 ± 0.02, respectively. The equivalent circuit of a bulk device fabricated from such material is derived and verified through small-signal RF measurements which, in addition, directly yield the high-field differential mobility and electron diffusion coefficient of the material. Operated as a microwave switch, isolation levels in excess of 20 dB with 4-dB insertion loss are reported at X-band with GaAS <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1-x</inf> P <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</inf> devices. It is shown that contact resistance can present serious limitations, although refinements in contacting technology should result in improved performance, making devices useable through millimeter-wave frequencies. Switching speed, the measurement of which is limited by laboratory pulse generation and detection capabilities, is estimated to be well under 200 ps and a theoretical limit of 20 ps has been predicted. The importance of this work lies in the fact that these switching speeds can be obtained with no sacrifice of incident RF power-handling capability, since there is no minority-carrier charge storage in these majority-carrier devices. In addition, the devices are stable at their transit-time frequency due to the absence of negative differential mobility in the material.

Visible narrow-band dc electroluminescence

The need of low-voltage de electroluminescent devices that emit in the visible portion of the spectrum is well-recognized. Devices composed of p-n junctions of binary or ternary III-V semiconductors exhibit high injection-efficiency but have poor internal quantum-efficiency, particularly in the green where the eye-response is the greatest. Furthermore, the all-important consideration of contrast as a criterion for display-effectiveness makes luminescence in a narrow visible band all the more useful. Such narrow-bandedness is not present in a nonlasing mode of a III-V device.