Reverse Bias Characteristics Research Articles

Design calculations of reverse bias characteristics for microwave p-i-n diodes

The derivation of a set of design formulas for predicting the impedance of diffused p-i-n diodes as a function of reverse bias voltage is presented. The diode is divided into five regions, and appropriate approximations are made in each region to simplify the integration of resistive and reactive contributions to the total impedance. Using these formulas, curves of series resistance and capacitance versus voltage are computed for an experimental diode reported by Senhouse. The curves agree well with others obtained using more complicated methods of integration. In addition to being useful for design calculations, the formulas derived offer insight as to the effects of frequency on diode impedance and the relative contributions of the various regions of the diode to the total impedance.

Germanium‐Silicon Alloy Heterojunctions

Germanium‐silicon heterojunctions have been prepared by an alloy process. By controlling the impurity concentrations, abrupt junctions having widths from 6000Aå to as low as 80Aå have been realized. Forward and reverse bias characteristics of several typical heteroj unctions are presented. No Esaki effect was observed for thin heterojunctions (<100Aå). This is attributed to masking by an abnormally high excess current. This excess current is a tunneling current via defect states caused by the large dislocation densities present in the junction.

Internal Field Emission at Narrow Silicon and Germaniump−nJunctions

A detailed study has been made of the reverse characteristics of several silicon and germanium alloyed $p\ensuremath{-}n$ junctions with breakdown voltages in the range of about 0.1 to 0.8 volt. In these junctions the reverse current is generated almost entirely by internal field emission (tunneling). The reverse bias characteristics are insensitive to the dislocation density present so that the tunneling current occurs mainly in undistorted material. From capacitance studies it is established that these narrow junctions are very close to being ideal step junctions. The room-temperature reverse characteristics are analyzed in terms of the usual tunneling probability expressions and in particular, good agreement, both qualitative and quantitative, is found between experiment and theory. The tunneling probability $\mathrm{exp}(\ensuremath{-}\frac{\ensuremath{\alpha}{\ensuremath{\epsilon}}^{\frac{3}{2}}}{E})$, when compared with experiment, yields values for $\ensuremath{\alpha}{\ensuremath{\epsilon}}^{\frac{3}{2}}$ in agreement with the theoretical ones to within a factor of less than 2 for both silicon and germanium.The critical voltage (the reverse bias voltage necessary to maintain a constant tunneling current) was measured as a function of temperature from 4.2\ifmmode^\circ\else\textdegree\fi{}K up to temperatures as high as 700\ifmmode^\circ\else\textdegree\fi{}K. In germanium, the critical voltage drops monotonically as the temperature increases whereas in silicon, there is considerable structure in the curve. This is shown to be consistant with the tunneling being by direct transitions in germanium and by indirect transitions (involving phonon emission and absorption) in silicon. In germanium, the temperature dependence of the critical voltage arises from that of the direct energy gap while in silicon, it is determined, primarily, by the available phonon density. From an analysis of the temperature data for silicon that invokes the transverse acoustic phonons, the estimate of $\ensuremath{\alpha}{\ensuremath{\epsilon}}^{\frac{3}{2}}$ that is obtained is in excellent agreement with that found, independently, from the analysis of the reverse characteristics.