Charge-packet-initiated switching of metal—tunnel-oxide—silicon (MTOS) junctions

We report the switching of a bistable metal-tunnel-oxide-silicon (MTOS) junction from a low-current state to a high-current state by the insertion of a charge packet of minority carriers from a charge-coupled device input structure. For the 33-Å tunnel oxide reported in this letter, a switching threshold of 630 pC for a 40 mils²device area was observed. The transient switching time is approximately 10-100 ms, depending upon the size of the injected charge packet.     

Status of the GaAs metal—oxide—semiconductor technology

A review of recent and current work on GaAs insulated-gate technology is presented. First, various techniques for the formation of heteromorphic and homomorphic dielectrics are outlined and some important aspects of properties of these dielectrics are reviewed. Second, MOSFET structures, fabrication procedures, and microwave performance are described. Third, the application of GaAs MOSFET's to digital integrated circuits is summarized.     

Limited reaction processing: In-situ metal—oxide—semiconductor capacitors

Limited reaction processing (LRP) has been used to fabricate in-situ silicon-silicon dioxide-polycrystalline silicon layers for metal-oxide-semiconductor (MOS) capacitors. The process consists of multiple in-situ rapid thermal processing steps to grow or deposit different layers. Capacitors have been fabricated from these layers and analyzed by capacitance-voltage measurements for interfacial fixed charge and interface state density. The capacitors exhibit excellent characteristics.     

A low-voltage alterable EEPROM with metal—oxide-nitride—oxide—semiconductor (MONOS) structures

Theoretical and experimental investigations to obtain lower voltage electrically erasable and programmable ROM's (EEPROM's) than conventional devices have been performed. The scaled-down metal-oxide-nitride-oxide-semiconductor (MONOS) structure is proposed to realize an extremely low-voltage programmable device. The proposed scaled-down MONOS devices enjoy several advantages over MNOS devices, e.g., enlargement of the memory window, elimination of degradation phenomena, and drastic improvement in device yield. Low-voltage operation with ± 6-V supplies is demonstrated by the fabricated scaled-down MONOS transistors.     

Monolithic integration of a metal—semiconductor—metal photodiode and a GaAs preamplifier

A metal-semiconductor-metal (MSM) photodiode and a preamplifier have been monolithically integrated on a GaAs substrate by a very simple fabrication process. Measurements have shown that the constituent MSM photodiode has a sensitivity of 2.2 A/W and a -3-dB cutoff frequency of as high as 1 GHz. The present photodiode has been found to realize an extremely high photosensitivity of the monolithically integrated circuit, 26 mV/µW.     

On the study of metal—Semiconductor contacts

An iterative error-minimizing multiparameter computer technique is used to establish values for a six-parameter model of a metal-GaAs barrier based on measurements of temperature, current and the voltage split resulting from rectification at the contact. The most important feature of the technique is that it is not necessary to make assumptions regarding contact area, effective electron mass, and barrier heights. Rather, these parameters emerge from the computation as best-fitting computed values. The agreement between the computed contact area and the known physical electrode area is taken as an indicator of the validity of the procedure and of the consistency of the experimental data. Thermionic-field emission theory is proved quantitatively correct using this technique. Also, this technique constitutes a new method of establishing the value of the effective electron mass. For GaAs m* = 0.0677.     

Low-frequency excess noise in metal—Silicon Schottky barrier diodes

Theoretical models for the generation-recombination noise and trapping noise in metal-semiconductor Schottky barrier diodes are developed. Low-frequency excess noise in Schottky barrier diodes is found to be dominated by the modulation of the barrier height φB caused by fluctuation in the charge state of traps or generation-recombination centers. This noise mechanism does not occur in p-n junctions. The bias and the temperature dependence of the generation-recombination noise is critically compared with the experimental data for forward diode current ranges from 3 to 300 µA and operating temperatures from -25° to 100°C. Trapping noise in Schottky barrier diodes is observed at low temperatures in diodes not intentionally doped with deep level impurities. The experimental results on trapping noise can be described by assuming that the trap states have a constant capture cross section and are uniformly distributed in space, as well as in energy. The surface potential at the diode periphery also has an important effect on the Schottky barrier diode noise. The best low-frequency noise behavior is found when the surface is at the flat-band condition. An accumulated surface is always associated with a large amount of low-frequency excess noise.     

Impedance measurement of the illuminated metal—SiO2—Si diodes

Impedance measurement of light-illuminated MIS diodes was made. It becomes clear from the results that in the inversion region conductance of the MIS structure is more sensitive to illumination than its capacitance and that negative photoconductivity appears at low frequency, which is explained by the theory of Grosvalet et al.     

Properties of ion-implanted junctions in mercury—cadmium—telluride

The formation of n-p junctions by ion-implantation in Hg0.71Cd0.29Te is shown to be a result of implantation damage. n-p photodiodes have been made by implantation of Ar, B, Al, and P in a p-type substrate with acceptor concentration of 4 × 10¹⁶cm^-3. The implanted n-type layer is characterized by sheet electron concentration of 10¹⁴to 10¹⁵cm^-2and electron mobility higher than 10³cm². V^-1. s^-1, for ion doses in the range 10¹³-5 × 10¹⁴cm^-2. The photodiodes have a spectral cutoff of 5.2 µm, quantum efficiency higher than 80 percent, and differential resistance by area product above 2000 Ω . cm²at 77 K. The temperature dependence of the differential resistance is discussed. The junction capacitance dependence on reverse voltage fits a linearly graded junction model. Reverse current characteristics at 77 K have been investigated using gate-controlled diodes. The results suggest that reverse breakdown is dominated by interband tunneling in field-induced junctions at the surface, for both polarities of surface potential.     

Effects of contact resistance and dopant concentration in metal—Semiconductor thermoelectric coolers

The maximum heat that can be pumped by a metal-semiconductor thermoelectric cooling stage depends strongly on the dopant concentration in the semiconductor and on contact resistance at the metal-semiconductor interface which is cooled. A comparison is made between theoretical models describing these effects and experimental data for GaAs, both taken from original measurements and compiled from the literature. A convenient, new technique for determining the Peltier coefficient and the contact resistance of a metal-semiconductor contact is described. The results indicate that, in the case of GaAs, Au:Ge:Ni alloy contacts are effective in minimizing the contact resistance.     

Current—Voltage characteristics of bulk semiconductors on impact ionization

A simple theoretical model based on the concept of impact ionization of carriers is worked out to represent the current-voltage characteristics of bulk semiconductors. The underlying idea is that the carriers start attaining velocity saturation and multiplying themselves soon after acquiring a minimum energy required for impact ionization. Consequently, in a certain region of the device the rate of decrease of resistance with the increase of carrier concentration becomes very high giving rise to negative resistance. The above model agrees fairly well with the experimental results.     

The optimization of metal—Insulator—Metal nonlinear devices for use in multiplexed liquid crystal displays

This paper describes the steps taken in the optimization of metal-insulator-metal (MIM) nonlinear devices for use in multiplexed liquid crystal displays. Circuit modeling and computer simulations were used to establish the capacitance and current versus voltage characteristics of the ideal MIM. By controlling processing parameters such as nitrogen doping and anodization voltage, device characteristics can be brought into the optimum range.     

Avalanche injection delay in Lo—Hi junctions and the ionization rate at low electric field

Delay time in the avalanche injection is observed in Lo-Hi junctions of n- , p-silicon and germanium. The measured delay time gives an estimate of the electron ionization rate at low electric field.     

Edge inversion channels and surface leakage currents in high-voltage semiconductor devices

It is shown that the electric field over the surface of semiconductor devices can be sufficient to induce edge inversion channels if the bias voltage is high and the surface charge density Q _s is low. In this case, the edge region of the devices containing the p-n-p structure (e.g., that of thyristors) functions as a planar p-channel MIS transistor with a combined gate and drain and the entire medium over the surface functions as the gate insulator. The current between the source and drain of this “edge MIS transistor” is the surface leakage current of the entire device. An analytical theory describing the current-voltage characteristic in the subthreshold mode is developed. It is shown that this new mechanism controls the total leakage current of high-voltage devices if |Q _s | and temperature T are small enough (|Q _s | < 4 nC/cm², T < 270 K and |Q _s | < 58 nC/cm², T < 600 K for silicon and silicon carbide devices, respectively).     

Transport across a high—low barrier and its influence on specific contact resistivity of a metal—n-GaAs ohmic system

Thermionic emission is hypothesized as a mechanism of carrier transport across the high-low barrier of a metal-semiconductor (M-S) ohmic junction. The barrier resistance, based on this theory is calculated and combined with tunneling resistance of the M-S junction to evaluate specific contact resistivity of ohmic contact to n-GaAs. The theoretical results interpret the published experimental data convincingly and thus validate the proposed mechanism of thermionic emission.     

Potential distributions in metal—Semiconductor and p-i-n structures on a-Si:H by capacitive techniques

C(0),fandC-V-fcharacteristics have been used to find the barrier profile and depletion width in several Schottky (i-n⁺) structures on a-Si: H. Depletion widths for Pd and Cr Schottky structures are estimated to be around 0.28 and 0.21 µm, respectively. DarkC-Vmeasurements on these structures do not show the trends expected from the semiconductor behavior of theIregion. Instead, trap controlled current conduction in theIlayer fits the darkC-Vcharacteristics. DarkI-Vdata further support this observation. Trends in the capacitance measurements on p-i-n structures have also been explained on the basis of the above model.     

Low electric field hole impact ionization coefficients in GaInAsand GaInAsP

The electric field dependence of the hole impact ionization coefficients in Ga_0.47In_0.53As and Ga_0.28 In_0.72As_0.61P_0.39 was obtained from the electrical characteristics of p-n-p heterojunction bipolar transistors. The anomalous low field behavior of the electron impact ionization coefficients in these materials was not observed for the case of holes. Within the accuracy of our measurements me observed no change in the hole ionization rates in the temperature range of 20 to 120°C     

Small-signal impedance of avalanching junctions with unequal electron and hole ionization rates and drift velocities

A small-signal analysis of an avalanching semiconductor junction is presented for unequal electron and hole ionization rates and saturated drift velocities. The model consists of a thin ionization layer in a thicker depletion layer. The ionization rates are assumed independent of distance in the ionization layer and zero elsewhere. This analysis is an improvement of Read's, and is sufficiently realistic to predict most of the small-signal characteristics shown by the computer analysis of Misawa. The linearized differential equations describing the ionization layer are solved with the ionization rates perturbed by the ac electric field. The ac junction impedance is calculated from the solutions of the differential equations. Although the small-signal analysis does not predict the conversion efficiency of an avalanche diode oscillator, it does predict the threshold conditions for oscillation. It may also help predict the conditions for maximum efficiency through knowledge of the input power and the Q of the diode at the onset of oscillation.     

The maximum zero-voltage tunnel current and its fluctuations for lead—lead oxide—lead Josephson tunnel junctions

The maximum zero-voltage tunnel current I0and its fluctuations were measured for Josephson tunnel junctions as a function of the normal state resistanceRin the range of 50-300 Ω atT = 4.2K. The junctions, based on pure lead, have areas of about 100 µm², corresponding to capacitancesCof about 3 pF. The results obtained from a simple noise model, describing the junction in the zero-voltage state as a parallel resonant circuit with parametersC, L sim Phi_{0}/2piI_{0S}, andR, are in good agreement with the experiments. It is shown that the deviation of the experimental results for high-resistivity junctions from the theory of Ambegaokar and Baratoff is due to thermal noise currents originating in the normal state resistanceR.     

Modeling and measurement of bistable semiconductor lasers

A theoretical model of bistable semiconductor lasers (BSL) under optical triggering is proposed, which takes into account the amplification and absorption processes in the laser structure. It has been found that the main factor limiting the highspeed operation of BSLs is the carrier lifetime in the absorber. A novel solution has been proposed consisting of bombarding the absorber with a proton beam. This paper presents the first experimental and theoretical results on the transition time and the turn-on jitter of such a BSL with optical triggering. Measurements on bulk and multiple quantum well BSLs revealed the dependence law of transition time and turn-on jitter on the injection currents. It has been found that, for a constant current in one active section, the rise time decreases but the fall time increases with injection current in the other section. An optimal current value can then be found to minimize the overall transition time. The measured turn-on jitter and relaxation oscillation period decrease with increasing injection current, in good agreement with theoretical predictions. 2.5 Gb/s optical triggering with a bit-error-rate less than 10^-9 is demonstrated, for the first time, by using such a BSL without electrical reset