Silicon p−n insulator-metal (p-n-I-M) devices

Silicon p-n-I-M devices with thin insulating layers ($\text{thicknesses}\text{? 30}\text{A}\text{?}$), named MTIS devices, have been developed. The two terminal device shows an S-shaped negative resistance characteristics similar to a Schockley diode (or p-n-p-n diode). Typically the threshold and sustaining voltages are 10 ～ 15 and 1.3 ～ 2 volts, respectively. The former however can be controlled by optical illumination. Turn-on time including delay is less than 2 nsec and turn-off time ? 1 nsec or less. A thyristor-like device with its third terminal connected to the n-layer shows switching operation controllable by this terminal. A monolithic linear array of p-n-I-M diodes with 30 μm spacing operates as a shift register through coupling of adjacent diodes. Life of the two terminal devices recorded at present is over 1.5 × 10⁴ hr. These devices can be applied to low power and high-speed electrical switching and also to optical switching and integrated logic circuits.     

Hot photo-carrier and hot electron effects in p-n junctions

When a p-n junction of semiconductor (with bandgap energy E_g) is illuminated by light beam (with photon energy hv) in the condition of E_g>hv, such as in Ge p-n junction illuminated by CO₂ laser beam, an electromotive force (emf) was induced between the terminals of the p-n junction, which indicated the opposite polarity to the ordinary photovoltaic effect like a solar cell. Such an anomalous photovoltaic phenomenon was explained by an optically excited hot carrier effect, through the following experiment with electrical excitation. Using a rod of n- or p-type Ge with a p-n junction at the surface of its center and an ohmic contact at each terminal of the rod, the same kind of phenomena was observed when electric field is applied along the length of the rod. The perpendicularly induced voltage or current had the same polarity instead of the reverse change of the applied electric field, and increases with increasing the applied field strength. The perpendicularly induced emf was caused by warm or hot carriers crossing the potential barrier of the p-n junction, which is very sensitive to the departure from thermally equilibrium velocity distribution of carriers.     

Impact ionization wave breakdown of drift step recovery diodes

High frequency IMPATT oscillations followed under certain conditions by reversible impact ionization wave breakdown of the p ⁺-n-n ⁺ diode structure have been experimentally observed for the first time in a drift step recovery diode operating in the avalanche breakdown mode after a fast voltage restoration of the p-n junction.     

A thyristor protected against di/dt failure at breakover turn-on

The principle and the operation of a thyristor that can be turned on by exceeding its breakover voltage are described. The principle uses the concept of an auxiliary thyristor amplifying the small breakover current to a large gate current for the main thyristor. In this arrangement the breakover turn-on has to occur first in the auxiliary thyristor. This is ensured by a doping of the n-base of the auxiliary thyristor which is higher than that of the n-base of the main thyristor. Time resolved infrared photographs of the breakover turn-on are presented. Also, infrared photographs of the breakdown radiation from p-n-p structures are used to give a survey on the starting silicon which already contains the inhomogeneous doping.     

A simplified theory of the p-i-n diode

A simplified theory of the p-i-n diode is developed for the case of heavy injection in the base, and light injection in the end regions. The current I is taken as the fundamental parameter. The carrier densities n₁ and n₂ at the base boundaries are given directly as functions of the current I by means of simple approximate expressions. The approximation improves with increasing base width and increasing current. It is always within 15% of the correct value for base widths of about 2 diffusion lengths or higher. The accuracy is much better still on the voltage drop across the device, as calculated from the approximate equations for the carrier densities within the base.     

Carrier temperature effects in a p−n junction

Carrier temperature effects arising in a p?n junction are discussed by solving a chosen set of conservation equations. An analytic solution is found for the current flow assuming small departures of the carrier temperature from equilibrium, and a numerical solution involving large carrier temperature variations is presented. The reverse bias at which avalanche breakdown is predicted for a germanium diode is in agreement with experiment.     

Breakdown walkout in planar p-n junctions

Junction breakdown walkout in p-n junctions has been investigated in this paper. It has been shown that walkout is closely related to the avalanching in the junction. During the time the junction is subjected to the reverse breakdown, because of avalanching, hot electrons are generated in the depletion region. Some of the hot electrons have enough energy to cross the oxide-silicon barrier and to go into the conduction band of the oxide. The electrons are trapped in the traps and charge the oxide negatively, resulting in reduction of electric field intensity in the surface depletion region of the p-n junction. This results in an increase of the breakdown voltage. A theory has been developed to explain hot electron injection and trapping in the oxide and its effect on the breakdown voltage. A comparison of results predicted by theory, with the experiments has also been carried out.     

Characterisation of linearly graded p-n junction

Electrostatic potential, carrier densities and space charge density distributions have been calculated using an iterative scheme for linearly graded p-n junction. It is found that the results obtained from this scheme are close to those given by rigorous numerical formulations, especially at applied forward bias. As an application of this scheme the charge-defined emitter space-charge-layer transit time has been calculated and results compared with those of numerical algorithms.     

Equivalent circuits for transients in p-n junctions and solar cells with their application to methods for minority carrier life-time measurements

Equivalent circuits corresponding to series solutions obtainable under various operating conditions of p-n junctions and solar cells are given. These circuits are directly applicable to the small signal impedance measurements. The transient behaviour of the p-n junction devices during minority carrier lifetime determination experiments has also been explained successfully with the help of these circuits. This provides a better insight towards the physical processes involved in these methods and interpretation of the various experimental results becomes easier.     

Some investigations on secondary breakdown in p-n junctions considering the effect of thermally generated carriers

The V-I characteristic of a p-n junction under breakdown is calculated taking the thermally generated carriers into account. The current density distributions computed under different conditions have been given. The light emission and other characteristics reported by Chiang and Lauritzen and others have been explained.     

Boundary conditions at p-n junctions

A discussion is presented of the relationships between carrier densities at a p-n junction and the junction potential. The major purpose of the work is to discuss the relationship between the Fletcher and Misawa boundary conditions. In addition, a discussion is presented of an extension of the normal boundary conditions to account for current flow within the junction space charge region.     

An extension of the ideal diode analysis for the heavily doped p-n diode

In this paper, an extension of the ideal-diode analysis for the heavily-doped p-n junction diode is proposed. The heavy doping effects such as carrier degeneracy and band gap narrowing are accounted for by using a tractable empirical approximation for the reduced Fermi-energy given by[12] and employing effective intrinsic density. Under the assumption of low-level injection, it is found that the injected minority-carrier current, and the charge storage in the quasi-neutral regions should depend exponentially on values of F(Y), where F(Y) is a function of dopant dentisy at the depletion edge of the quasi-neutral emitter (or) base region of the p-n junction. Results of our calculations of excess hole current for the short base and the long-base diode show significant change from the values predictged by the conventional diode theory.     

Theoretical calculations of Debye length,built-in potential and depletion layer width versus dopant density in a heavily doped p-n junction diode

Theoretical calculations of Debye length, built-in potential, depletion layer width and capacitance as a function of dopant density in a heavily doped p-n junction diode are described in this paper. The heavy doping effects such as carrier degeneracy, dopant density-dependent dielectric constant and bandgap narrowing are accounted for by using the empirical approximation for the reduced Fermi-energy given by[1] and the dopant density dependent dielectric constant given by[2], as well as the bandgap narrowing model proposed by[3]. The results show that: (1) bandgap narrowing and carrier degeneracy have important effects on the junction built-in potential; (2) carrier degeneracy and dopant density-dependent dielectric constant are important to Debye length for the abrupt junction case, and (3) the dopant density-dependent dielectric constant is a key parameter which strongly affects the values of depletion layer width and depletion capacitance. These findings are important for modeling of heavily doped p-n junction devices in the VLSI applications.     

High-voltage planar junction with a field-limiting ring

A twodimensional Poisson equation is solved as part of a program to improve breakdown characteristics of a planar p-n junction by using a field limiting ring. The influences of n^? concentration and n^? layer width of p⁺-n^?-n⁺ diode are investigated. Higher n^? concentration and smaller n^? width make optimum distance between anode and field limiting ring smaller. Breakdown voltages predicted by optimising method reported agree well with the experimental results.     

Harmonic distortion in a one-dimensional p-n-p transistor

A method to obtain nonlinear distortion of small a.c. signals in a one-dimensional bipolar transistor is described. The fundamental physical semiconductor equations are the basis from which the small-signal relations are derived. A finite difference scheme is employed to achieve space-discretization; temporal dependence of input-output relations is given in terms of Volterra functional series. The internal distribution of quasi-Fermilevels, potential and excess carrier densities is discussed and some computational results are produced. The influence of frequency, bias point, and external circuit elements on distortion properties is illustrated. Throughout, a common-emitter p-n-p transistor structure is assumed. The theory of Volterra series analysis is briefly summarized.     

Effect of double reflection on the forward current-voltage characteristics of a silicon p+-s-n+ epitaxial diode

The behaviour of both majority and minority carriers in a p⁺-s-n⁺ epitaxial diode (where s may be p or n) has been investigated in this paper. Forward current-voltage characteristics of the diodes are obtained by exact numerical analysis, taking into account the effects of energy-gap narrowing, Auger recombination and carrier-carrier scattering. As with previous authors, it is found that the forward current increases with increasing middle layer thickness. The present analysis shows that such increase occurs only upto a specific applied bias, after which the forward current decreases with increasing middle layer thickness. This behaviour is attributed to double reflection, i.e. the reflection of both majority and minority carriers by the p-n junction and high-low junction respectively. Beyond the specific bias so determined, junction reflection loses its effectiveness. Distribution of carrier concentration and junction voltages for several device configurations are given to illustrate these features. The majority carrier reflection by the p-n junction is found to have a dominating effect in all cases.     

Influence of doping the base surface on parameters of a bipolar dual-collector lateral magnetotransistor

The effect of sensitivity inversion of magnetotransistors is studied using an instrument-technological simulation. The comparison of simulation results and experimental data enabled us to determine relations between sensitivity signs and distributions of injected charge carrier flows in structures of bipolar dual-collector lateral n-p-n magnetotransistors, the base of which is a diffused well (3CBMTBW). It is determined that the 3CBMTBW magnetotransistor with a small surface recombination velocity at the silicon-silicon dioxide boundary and with extraction of injected electrons by a base-well (substrate) p-n junction that is distant from the surface enables us to obtain a high sensitivity of 11 V/T at a good reproducibility and stability of parameters.     

High quality thick epitaxial films for power semiconductor devices

High quality epitaxial layers with low defect levels are the key to fabrication of high voltage power devices. Growth of 100 μm thick epitaxial layers has been performed using a thermally driven chemical vapor deposition process. Three important parameters that have significant influence on epitaxy quality have been identified: substrate surface condition, reactor system cleanliness, and deposition process. The prerequisite p-n-p structure of a 6 kV thyristor was fabricated using 100 μm thick epitaxial layers to form the p-base. Defect density (hillocks and dislocations) in epitaxial layers has been correlated with the breakdown voltage of the p-n-p structure. It was found that an order of magnitude improvement of the defect level was obtained using well polished substrates instead of poorly polished substrates. Further improvement was achieved with the use of an etched reactor system before epitaxial growth, resulting in the reduction of defect density by another order of magnitude. A new cycled process, consisting of successive H₂ purges and deposition steps, is proposed that effectively reduces the defect level by an additional factor of 4, as compared with the conventional continuous deposition process. Specular epitaxial layers without spikes were obtained. Experimental results showed that for thick epitaxial films (100 μm), a susceptor with round-bottomed depressions provides higher dislocation density than one with flat-bottomed depressions, leading to a lower breakdown voltage of test devices.     

Properties of Mn-doped p-type InxGa1-xAsyP1-y grown by liquid-phase epitaxy

Epitaxial layers of p-type In_xGa_1-xAs_yP_1-y doped with Mn were grown by liquid-phase epitaxy on (111)-B oriented InP substrates at a growth temperature of 635°C. The doping characteristics and electrical and luminescent properties were studied and compared with those in Zn-doped epilayers. The distribution coefficient of Mn was about 0.1–0.3. The p-type epilayers with hole concentration of up to 3 × 10¹⁸ cm^?3 could be easily obtained by Mn doping. The activation energy of the Mn acceptor was about 40 meV. Mn doping yielded a broad photoluminescent emission spectrum which probably arises from d-shell interaction of the Mn as well as strong phonon coupling. From electron beam-induced current measurements in p-n heterojunctions utilizing Mn, a value of L_n = 2 μm was obtained for the minority carrier diffusion length of electrons in the p-type region.