Carrier heating effects in junctions at very low currents

The effects of carrier heating by the electric field are analysed in abrupt $\text{p-n}$ junctions at very small currents. Two features, which are usually neglected, are shown to be of importance. (a) The heat transported by the carriers plays an appreciable part in the energy balance equation, which determines the carrier temperature. (b) The current has, in the junction and in the neighbourhood, two important additional components, one being due to a correction of the diffusion current, and the other being proportional to the gradient in the temperature of the carriers.     

Carrier trapping and recombination in avalanche diodes

The differential equations describing an avalanching p⁺nn⁺junction in the presence of multiple-level carrier traps have been solved numerically for trap densities as high as two orders of magnitude greater than the n-region background doping. The results compare quantitatively with a number of past, as well as new, experimentally observed changes in avalanche microwave diode performance with neutron damage. In particular, trapped charge in the space-charge region tends to localize the avalanche region near the p⁺n junction, which raises the frequencies of operation. Carrier trapping at the edges of the space-charge region explains the increase in operating voltage and decrease in small-signal capacitance. The localization of the avalanche region, through carrier trapping in the space-charge region, and recombination effects at high avalanche current densities combine to cause eventual RF failure of IMPATT and TRAPATT diodes with neutron damage.     

Carrier radiation distribution in organic light-emitting diodes

This paper is based on the analysis of white organic electroluminescent device electroluminescent spectrum to explain the regular pattern of carrier radiation distribution.It has proved electron that is injected from cathode is satisfied with the regularity of radiation distribution on the organic emitting layer.This radiation distribution is related to several factors,such as electron injection capabilities,applied electrical field intensity,carrier mobility,etc.The older instruction design is ITO/2-TNATA/NPB/ADN:DCJTB:TBPe/Alq3/cathode.Get to change electron injector capabilities through using different cathode and also find electroluminescent spectrum to produce significant changes.Simultaneously,electron radiation quantity has some limitation,and electroluminescent spectrum reflects that spectral intensity does not change anymore when the ratio of cathode dopant to a saturated state on the organic emitting layer.It also shows the same spectrum variational phenomenon while changing the applied electrical field intensity.To put forward of the carrier radiation distribution is good for organic light emitting diode (OLED) luminescence properties analysis and research.     

Carrier heating or cooling in semiconductor devices

A theory of charge and energy transport by hot or cold carriers in inhomogeneous semiconductor structures, developed earlier, is presented here in extended form under the assumptions of a simple parabolic band model, elastic or velocity-randomizing scattering processes and one-dimensional devices with steady-state flow of charge and energy. The treatment begins with the derivation of a relation between the two first terms in the Legendre expansion of the distribution function and the definition of the relaxation times for the two types of scattering processes mentioned. Subsequently, the expressions for the current density and the energy flux are obtained for an arbitrary shape of the isotropic part of the distribution function, so that they are valid for hot or cold carriers. In these expressions appear four transport coefficients, namely the mobility, the diffusion coefficient, the thermal mobility and the thermal diffusion coefficient. Furthermore, under the assumption of a Maxwellian form of the isotropic part of the distribution function, the obtained expressions are simplified. Generalized Einstein relations between the transport coefficients are derived and the boundary-value problem is formulated which has to be solved in order to determine quantitatively the behavior of a device if the carriers become hot or cold. Finally, a discussion is given of a similar theory by Stratton as well as of limitations, advantages and possibilities of applications of the present theory. The present synthesis is not available elsewhere.     

Carrier transport in the drift region of read-type diodes

The transport properties of the drift region significantly impact the conversion efficiency of Read-type IMPATT diodes. A detailed numerical study has been undertaken to gain insight into the carrier transport under large-signal conditions and the roles of depletion-width modulation and the carrier-induced electric field. A phase delay in the peak of the avalanche current results from assuming a sinusoidal voltage rather than a sinusoidal field and is incorporated in the model. induced current waveforms, transport factors, diode admittances, and conversion efficieneies are presented as functions of RF level, bias current density, and the small-signal transit angle. A region of partial collection of the drifting carriers exists between regular IMPATT operation and the onset of the premature collection mode, which provides a smooth transition between these two modes. The effects of premature collection are most pronounced at long transit angles where the corresponding large increase in the transport factor at a high RF level will give high-efficiency operation, but also a large hysteresis in the tuning characteristic. The displacement current has an appreciable effect on the induced external current under these conditions. The presented results aid the understanding of tuning behavior and tradeoffs in design for Read diodes.     

Carrier lifetime measurement by ramp recovery of p-i-n diodes

A method for measuring carrier lifetime in the base of power p-i-n diodes is introduced. The method is based on ramp recovery of power diodes. Neither the charge left at the end of the first phase of the recovery process, nor the based width are needed to determine lifetime. Moreover, information about the base width of relatively short-base diodes can be obtained     

Contact effects in Gunn diodes

This letter shows how the splitting of the forward and reverse current/voltage curves of a Gunn diode may be interpreted in terms of different models of contact damage, and proposes a simple test technique to obtain a quantitative measure of contact quality. Experimental verification of this technique is presented, showing a correlation between device efficiency and a contact parameter ?.     

Effect of junction heating on the magnetocurrent in semiconductor diodes†

The effect of junction heating on the temperature dependence of magnetocurrent in semiconductor diodes is explained by taking into account the temperature dependence of various diode parameters.     

Radiation effects in transit-time microwave diodes

There has been considerable progress in the direct generation of microwave power using two-terminal semiconductor devices during the last decade. Permanent and transient radiation effects on bulk (Gunn and LSA) and junction (IMPATT, TRAPATT, and BARITT) transit-time microwave diodes are reviewed. Emphasis is placed upon relating the primary effects of radiation to the physics of device operation. The principal permanent damage is attributed to carrier removal effects, impairing the RF performance of bulk diodes below 10¹⁴neutrons/cm²and junction transit-time diodes at fluences near 10¹⁵neutrons/cm². The principal transient effect is the generation of free carriers by ionizing radiation, affecting the RF performance of bulk diodes above 10⁹rad/s and junction transit-time diodes at dose rates near 10⁸rad/s.     

Distributed effects in large-area Esaki diodes

General expressions have been derived for the impedance of rectangular and circular Esaki diodes which take account of the distributed nature of diodes with large-junction area. These expressions have been used to calculate the diode dimensions for which self-supporting internal oscillations can occur. Simple expressions have been derived for the series-parasitic impedance of diodes with smaller transverse dimensions.     

Temperature effects in silicon avalanche diodes

Gain-voltage curves for reach-through avalanche photodiodes are computed using the ionization rate data of van Overstraeten and de Man and Lee et al. and compared with measured curves. Noise spectral density measurements are also made and compared with McIntyre's avalanche noise theory. Agreement between computed and measured k-values as obtained from the noise measurements and between the computed and measured gain-voltage relationship can only be obtained with the ionization rate data of Lee et al. Gain-voltage curves were measured over the temperature range ?17 to +55°C and compared with computed curves in which temperature dependence of the ionization rate data of Lee et al. is computed using the modified Baraff theory. Excellent agreement between theory and experiment is obtained.     

Minority carrier effects in GaInP laser diodes

Using a top-contact window, we have observed emission from a direct-gap monitor layer placed at the interface between the p-cladding and contact layers of an AlGaInP laser diode when driven under forward bias, thereby providing direct evidence for minority carrier (electron) leakage in these devices. We have further shown that the leakage is due to both drift and diffusion and, using pulsed optical excitation of a device under bias, we have determined a value of 170±10 cm² V^-1 s^-1 for the mobility of minority carriers in the p-type cladding layer by a time-of-flight experiment. The data was analyzed using a simulation which takes account of the influence of recombination times in the well and monitor layer on the overall time response of the structure. The measured mobility corresponds to electron transport through the X-conduction band. We show that the drift component of the leakage current reduces the differential efficiency and is responsible for the decrease in external differential efficiency with increasing temperature. Because the leakage occurs by a mixture of drift and diffusion, the transit time does not decrease significantly with increasing drive current; however the impact of leakage on the modulation response is predicted to be very small unless the leakage becomes a substantial fraction of the total current     

Resonance and parametric effects in IMPATT diodes

The theory of nonlinear fundamental and subharmonic resonances in the avalanche region of IMPATT diodes is developed by use of the method of harmonic balance. Due to the high resonance strength of the subharmonic mode, and as a consequence of large-signal parametric interaction, the negative resistance of the diode is markedly increased at the presence of a self-pumped oscillation of twice the frequency of the fundamental mode, especially for low-transit angles across the drift region.     

Facet heating and axial temperature profiles in high-power GaAlAs/GaAs laser diodes

Degradation of the facets represents a major reason reducing the performance and the lifetime of high-power laser diodes. Nonradiative surface recombination of electrons and holes results in a strong heating of the facet region and subsequent defect accumulation. We theoretically investigated facet heating of an asymmetrically coated 20-stripe GaAs/GaA1As laser diode array by a self-consistent calculation of the axial profiles of temperature, carrier density, and optical intensity. To validate the model, we measured the facet temperature as a function of injection current using micro-Raman spectroscopy. Our results point to the possibility of catastrophical optical damage at the reflection-coated facet arising from the asymmetric thermal load of the facets.     

Circuit effects in second-harmonic tuning of IMPATT diodes

Two-frequency operation of IMPATT diodes is examined in this paper on a conceptual basis. It is shown that a simple interpretation of the "single-frequency" admittances of the diode may be made. An equivalent circuit is presented which shows that the effect of second-harmonic tuning is to introduce a nonlinear resonance into the fundamental input admittance. This occurs when the external circuit admittance is tuned to the neighborhood of the "single-frequency" oscillator admittance of the diode at the second-harmonic. Computer calculations of the tuned-harmonic mode, with the diode embedded in the simplest possible RF circuit, are presented to demonstrate the effect.     

Hot electron effects in single-injection silicon SCL diodes

A theory is presented on hot electron effects on the noise in single-injection SCL diodes. It is shown that the noise temperature T_n of such diodes can be written as T_n = T₀(1 + BV_a²), where T₀ is the lattice temperature, V_a the anode voltage and B a constant depending on the diode geometry and material constants. Experimental data presented for Si SCL diodes made on high-resistivity p-type material show excellent agreement with the theoretical expressions for T_n. Making certain assumptions, the measured values of B give a value of 1400 V/cm for the critical field strength E_c of high-resistivity p-type silicon.