Thickness Of Space Charge Layer Research Articles

Stress‐Induced Spectral Changes in Raman Spectra of n ‐ GaAs Encapsulated with Si3 N 4 Films

Raman spectra and wafer bending of encapsulated with films were observed. The stresses which are estimated from wafer bending by the Timoshenko relation depend on the thickness of encapsulated films. The changes in Raman spectra also depend on the film thickness. There is good correlation between the variation of the ratio of peak heights of longitudinal optical to coupled plasmon‐longitudinal optical modes in the Raman spectra, (LO/L‐), and the variation of stress deduced from wafer bending. The variation of the LO/L‐ modes with film thickness was explained by the change in space charge layer thickness and disordering by inhomogeneous strain.

Characterization of Pb3O4 films by electrochemical techniques

The band gap of semiconductor is determined by photovoltage spectrum. The photovoltage sign shows the semiconductor to be ofn-type conductivity. Mott-Schottky plot gives the position of Fermi level, the approximate position of band edges, donor density in the semiconductor and space charge layer thickness. The results agree with other reported values.

Characterisation of a-Si:H by complex impedance measurements

The electrical impedance of rf sputtered amorphous hydrogenated silicon has been measured in the sandwich configuration over the frequency range 5 Hz–500 kHz and temperature range 380–436 K. Complex impedance plots took the form of single half circles indicating that a-Si:H can be modelled as a parallel RC circuit. The centers of the half circles fall along a line angled at απ 2 rad from the real axis and the parameter α is shown to qualitatively measure the microscopic homogeneity of the a-Si:H samples. New evidence is presented for the formation of an interface space charge layer (thickness 0.06 μm) that occurred after the injection of carriers upon the application of a high electric field (10 5 V/cm).

Low-Resistance Ohmic Contacts to Zinc Selenide

A method of making low-resistance ohmic contacts to chemically cleaned ZnSe using In-Ga liquid alloy is described and the effect of alloying temperature on the contact characteristics has been investigated. Contacts annealed below 350°C are found to be non-ohmic. Above 350°C. ZnSe alloys with molten In and this results in ohmic contacts whose quality improves rapidly with temperature reaching an optimum for an alloying time of 1 minute at 400°C. Poorer contacts resultat higher temperatures. An explanation of these results is provided in terms of the heavily-doped regrown region thickness Xm and the space charge layer thickness Xd in ZnSe under the molten metals. It is found that ohmic contacts result only when Xm>Xd

Electroluminescence of heavily-doped heterojunctions pAlxGa1-xAs-nGaAs

There are given results of an investigation of the electroluminescence spectra of heavily- doped heterojunctions pAlxGa1-xAs-nGaAs prepared by liquid epitaxy, as well as some applications of a study of heterojunctions in the system AlAs-GaAs which have led to a creation of injection heterolasers with a low generation threshold at room temperature.In the heterojunctions pAlxGa1-xAs-nGaAs, due to a discontinuity in the conduction band ΔEc equal to the difference in the gap widths of the heterojunction components, one side injection can occur which facilitates an analysis of the mechanisms of current formation and electroluminescence. As shown by a study of the injection luminescence spectra of heavily-doped heterojunctions, depending on the thickness of space charge layer there can occur either thermoinjection filling of “tails” in the density of states in gallium arsenide or “diagonal” tunneling-recombination transitions directly between the electrons of the narrow-band and the holes of the wide-band heterojunction components. The radiation associated with “diagonal” transitions is polarized predominantly parallel to the electric field in the junction. An analysis of the dependences of radiation intensity on current and applied voltage indicates unambiguously an absence of a drop of the quasi- Fermi level at the heterojunction interface.Injection heterolasers representing n-p-p+ structures with heterojunctions in the system AlAs-GaAs have a threshold current density for the best specimens of ≈ 5 × 103 A/cm2 at 300 °K and internal losses of 3 cm-1. Low threshold currents at elevated temperatures and low losses can be attributed to inherent features of the heterolaser structure, viz. the regions of recombination and inverse population coincide and are located in the central narrow-band layer. This is why the recombination and light losses in the passive regions are very small.

Noise Analysis for a Silicon Particle Detector with Internal Multiplication

Internal carrier multiplication in a particle detector makes possible a reduction in the noise contribution of the following amplifier. The carrier multiplication, however, introduces additional noise from two sources. First, the statistical nature of the multiplication process gives rise to variations in the magnitude of the carrier multiplications. Second, as pointed out by Shockley, l the inherent statistical spatial fluctuations of impurity density within the space charge layer of a p-n junction lead to corresponding local fluctuations of the avalanche breakdown voltage Vb. At a bias below Vb this corresponds to local fluctuations of the multiplication factor M. The significance of both noise sources is evaluated. It is found that in general multiplication will improve the energy resolution only for the detection of low energy particles and for moderate values of M. The findings are illustrated by detailed calculations for a silicon junction having a breakdown voltage of 30 volts with a corresponding space charge layer thickness of 1.3 microns, appropriate for low energy particle detection.

Effects of Space-Charge Layer Widening in Junction Transistors

Some effects of the dependence of collector barrier (space-charge layer) thickness on collector voltage are analyzed. Transistor base thickness is shown to decrease as collector voltage is increased, resulting in an increase of the current-gain factor (α) and a decrease in the emitter potential required to maintain any fixed emitter current. These effects are shown to lead to two new elements in the theoretical small-signal equivalent circuit. One, the collector conductance (gc´), is proportional to emitter current and varies inversely with collector voltage. This term is the dominant component of collector conductance in high-quality junction transistors. The other element, the voltage feedback factor (μ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ec</sub> ), is independent of emitter current, but varies inversely with collector voltage. The latter element is shown to modify the elements of the conventional equivalent tee network.