Nonlinear electro-optic characteristic in a photoexcited semiconductor

We study the transport properties of a GaAs-based Gunn device under local optical excitation via direct numerical simulation. The simulation results show that the hysteretic transition in between quenched and transit modes. The key mechanism for this kind of transition is related to the formation of a stationary and nonuniform hole profile around the notch regime. Therefore, the development of optical control of the microwave output is reported. In addition, the influence of impact ionization on this nonlinear semiconductor is also discussed in the present study.     

Effect of temperature on the validity of the einstein relation in heavily doped semiconductors

An analytical expression of the modified form of the Einstein relation in heavily doped semiconductors in which Gaussian band tails are formed near the lower limit of heavy doping is derived for studying the temperature dependence of the diffusivity-mobility ratio of the carriers in such semiconductors. It is found that, with increasing temperature from relatively low values, the ratio first increases in a nonlinear manner and then decreases till, at high temperatures, it approaches its value corresponding to the non-degenerate condition resulting in a peak over a narrow range of temperatures.     

Electron and hole traps in N-GaAs crystals

Deep traps were measured and their electronic and optical properties were determined by junction capacitance techniques in n-GaAs crystals grown by different methods. Four electron-traps and four hole-traps were detected. An electron trap was not observed in LPE wafers. A hole trap at 0.45 eV above the top of the valence band was detected in all wafers measured here.     

A SOGICON type instability in silicon

A current oscillation phenomenon in SOGICON type Si device fabricated by the use of a planar process is studied. The oscillation is generated in the region between anode and notch which is located at the center on the sample. A considerably high electric field is observed in the notch region. Considering the hot-electron effect due to the high electric field, the mechanism underlying the current oscillation is discussed.     

Oscillatory effective mass in degenerate narrow-gap semiconductors in a quantizing magnetic field

An attempt is made to study the effect of a quantizing magnetic field on the effective electron mass in degeneraten-type narrow-gap semiconductors at low temperatures. It is found, takingn-Hg_1−x Cd _x Te as an example, that the effective electron mass shows an oscillatory magnetic-field dependence as is expected because of the dependence of the effective mass in degenerate non-parabolic bands on Fermi energy which oscillates with changing magnetic field. The amplitude of oscillations is, however, found to be significantly influenced by the alloy composition whereas the period is found to be independent of the band non-parabolicity, i.e. of the compositional parameter in ternary semiconductors.     

A model for the occurrence of transient negative photoconductivity in silicon doped with gold

A transient negative photoconductivity phenomenon observed in silicon doped with gold atoms has been investigated. On the basis of the trapping of photo-excited carriers into two deep levels of gold atoms, a model for the occurrence of transient negative photoconductivity is proposed and related qualitatively to some experimental results.     

MITATT mode in DDR heterostructure Impatt

Large signal characterisation of double heterostructure DDR Impatt diode has been carried out in the millimeter-wave range considering the MITATT mode of operation. The structure of the device is p⁺-p₂-p₁-n₁-n₂-n⁺ where impact ionisation and tunneling takes place in the p₁-n₁ region. In this study we have considered two well-known heterostructures, e.g., InP/GaInAs/InP and InP/InGaAsP/InP and one nonconventional structure GaAs/InP/GaAs. The theoretical results of the performances of these devices as regards of output power, efficiency, and negative conductance revealed that the structures are quite promising as the source of power in the millimeter-wave range. The analysis may be used for other mm wave DDR heterostructure Impatts.     

Conduction in short semiconductor structures

Low field mobility in short semiconductor structures decreases as a result of finite sample length. According to Kastalsky and Shur [1] the mobility scales down by a factor $\text{1 ?}\text{exp}\text{(}\text{?3η}\text{2}\text{)}$ where η is the sample length divided by the mean free path. From a solution of Boltzmann equation we show that the scaling factor is more accurately given by $\text{η}\text{(η + α)}$ where α is between $\text{4}\text{3}$ and 2. Mobility decrease can be simply interpreted in terms of a finite contact resistance.     

Electrical properties of p +/n + In0.53Ga0.47As tunnel diodes grown by liquid phase epitaxy

p ⁺/n ⁺ In_0.53Ga_0.47As tunnel diodes were prepared by liquid phase epitaxy and their electrical properties were characterized. These devices exhibit large forward conductances (2.59×10^{3 –1} cm^–2), high peak current densities (793 A/cm²) and large peak to valley current ratios (16.2). These devices offer great promise as intercell ohmic contacts (IOCs) for InP-based, onolithic multijunction solar cells.     

Thermal emission spectrum from a semiconductor electron-hole plasma

Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 55, No. 4, pp. 624–629, October, 1991.     

Electrical properties of p +/n + InGaAsP tunnel diodes with a bandgap of 0.95 eV grown by liquid phase epitaxy

p ⁺/n ⁺ InGaAsP tunnel diodes with a bandgap of 0.95 eV were fabricated by liquid phase epitaxy and their electrical properties were characterized. Forward conductances of 500 ^–1 cm^–2, peak current densities of 28.5 A/cm² and peak to valley current ratios of 14.3 were obtained at room temperature. These devices were incorporated successfully as Intercell Ohmic Connections (IOCs) for an InP-based, two-terminal monolithic multijunction tandem solar cell.     

Spatial structures of islands of electron-hole liquid in semiconductor quantum wells

The formation of the different structures of islands of electron-hole liquid in the quantum well is studied in a statistical model. The interaction between the islands of electron-hole liquid is considered by influencing of neighboring islands through exciton gas around the considered island. Two restricted regions were studied: an infinite strip and a disk. The theory gives the possibility to determine the probability of different states realization and to find the most probable state. The dependence of the radius, mutual positions of the electron-hole liquid islands, the number of the islands in the disk on the pumping, temperature and parameters of the system (the size and the shape) are calculated.     

Arsenic-implanted polysilicon layers

The diffusion behavior of implanted arsenic in polycrystalline silicon was investigated, using backscattering and electrical measurements. The diffusion coefficient isD=8.5×10⁻³ exp (−2.74/kT) for polycrystalline silicon deposited on freshly-etched silicon andD=1.66 exp (−3.22/kT) for the deposition on silicon having natural oxide. At the interface to the single-crystalline silicon, a pile-up of arsenic occurs, which depends also on the surface treatment prior to the deposition of the polycrystalline silicon.     

High-resolution positron lifetime spectrometer with BaF2 scintillators

A transient negative photoconductivity phenomenon observed in silicon doped with gold atoms by an appropriate diffusion condition has been investigated. The transient negative photoconductivity could be observed with a diode doped with gold atoms under intrinsic light-pulse illumination. In the recovery process of the transient negative photoconductivity to a steady-state dark level, two kind of time constants were observed, which may be related with the emission of electrons from gold level. A dependence of the magnitude of the peak value on the ambient temperature was observed; a qualitative explanation is given.     

In-situ formation of p-n junctions in semiconducting TiO2

Application of small voltages in the range from 0.5 V to 1 V to an originally homogeneously Fe-doped (0.5 mol-%) TiO₂ semiconductor at temperatures between 700° C and 750° C caused the formation of a p-n junction within the sample. This is indicated by a change of the U-I characteristics from a symmetrical to a diode type behavior. By inversion of the polarity of the applied voltage, the p-n junction could be removed. This process is completely reversible. The results are explained by an asymmetric change in the concentration of lattice defects, which act as dopants in addition to the extrinsic dopants, caused by the application of the voltage to the sample.     

Hot carrier effects in double injection phenomena

Carrier heating is shown to be responsible for unusualI(V) characteristics observed in small-sizep ⁺ nn ⁺ silicon on sapphire (SOS) devices. The classical quadratic law of the semiconductor regime becomes linear for high fields. The influence of dimensions and doping is experimentally checked and a model, based on the regional approximation method, is proposed. The key role is assumed by the hot-carrier region, growing from the cathode, where the electron and hole mobilities are field dependent: µ~E^–. A full agreement with the experiment in SOS is found for=0.5. The operating of hot carrierp ⁺ nn ⁺ devices can be described concretely with usual formalism by using the concept of effective carrier mobilities, which depend on the applied voltage.     

Current injected electron-hole plasma in GaP pin-device structures

We report first on an electrically generated electron-hole plasma (EHP) in GaP light emitting diodes having a pin-structure. For current densities above j ? 10³Acm^?2 and at T = 77 K a dense EHP is formed within the i-region whose carrier density can easily be changed by the injection level. The corresponding electron-hole pair densities n of the plasma and the resulting gap shrinkage ΔE_g have been determined using a least-squares fit of the EHP luminescence spectra. The lineshape analysis of the spectra yields a $\text{n}{}^{\mathrm{<mtext>1</mtext><mtext>4</mtext>}}$ -dependence of the gap shrinkage in quantitative agreement with findings from optically excited EHP and corresponding theoretical work. From electrical investigations it can be concluded that the EHP causes a strong nonlinear behaviour of the current-voltage characteristics.     

Dynamics of electron-hole plasma in semiconductor opening switches for ultradense currents

A physicomathematical model for calculating the dynamics of the electron-hole plasma in semiconductor opening switches for ultradense currents is developed. The model takes account of the real doping profile of a semiconductor p ⁺-p-n-n ⁺ structure and the following elementary processes in the electron-hole plasma: current-carrier diffusion and drift in high electric fields, recombination on deep impurities and Auger recombination, and collisional ionization in a dense plasma. The electrical pumping circuit of the opening switch is calculated by solving the Kirchhoff equations. The motion of the plasma in the semiconductor structure is analyzed on the basis of the model. It is shown that for ultrahigh pumping levels the interruption of the current in the opening switch occurs in the heavily doped regions of the p ⁺-p-n-n ⁺ structure and is due to saturation of the particle drift velocity in high electric fields. Zh. Tekh. Fiz. 67, 64–70 (October 1997)