William Paul Dumke

GaAsGaAlAs heterojunction transistor for high frequency operation

Abstract A bipolar transistor structure is proposed having application for either high frequency operation or integration with certain types of light emitting devices. The structure involves liquid phase epitaxially grown layers of GaAs for the collector and base regions, and of Ga1−xAlxAs for the heterojunction emitter. The high frequency potential of this device results primarily from the high electron mobility in GaAs and the ability to heavily dope the base region with slowly diffusing acceptors. The Ga1−xAlxAs emitter region provides a favorable injection efficiency and, because it is etched preferentially relative to GaAs, access to the base layer for making contact. Transistor action with d.c. common emitter current gains of 25 have been thus for observed. Calculations of the high speed capability of this transistor are presented.

BAND STRUCTURE AND DIRECT TRANSITION ELECTROLUMINESCENCE IN THE In1−xGaxP ALLOYS

The position of the (1, 0, 0) minima in InP are determined from measurements in the region of interconduction band absorption. Direct transition electroluminescence in the In1−xGaxP alloys is observed over a range of alloys up to x = 0.8 and photon energies of up to 2.2 eV at 300°K and is consistent with the bandstructure determined for InP and that of GaP.

Electron mobility in p‐type GaAs

The mobility of electrons in p‐type GaAs, μPn has been determined by measuring the common emitter cutoff frequency fT of heterojunction bipolar transistors with a wide, uniformly doped base. At 295 K, μPn =1150 cm2/(V s) is found for a hole concentration of 3.6×1018 cm−3. At 77 K, μPn =6000 cm2/(V s). The room‐temperature value is considerably smaller and the 77 K value considerably larger than the electron mobility in comparably doped n‐type material.

Current thresholds in stripe-contact injection lasers

Abstract A mathematical analysis has been made of the current distribution beyond the edge of the contact in a stripe contact injection laser structure. An analytical solution is obtained for this distribution using a simplified but reasonably accurate model. For a typical stripe-contact laser, the junction current beyond the contact region is equivalent to the current at threshold through an additional stripe width of the order of 10 μm. As a result of such current spreading, lasers with narrow stripe-contacts will have greatly increased apparent threshold current densities.

Band‐gap narrowing from luminescence in p‐type Si

The luminescence data of Schmid, Thewalt, and Dumke on heavily doped p‐type Si has been analyzed to provide the effective band gap for the n⋅p product at room temperature in p+Si. The results are in very good agreement with the measurements of Slotboom and DeGraaff, and extend the acceptor concentrations for which the effective band gap is available by a factor of four. The disagreement of these results with the values obtained from infrared absorption measurements is further evidence of a nonrigid band‐gap shift.

The effect of electron-hole scattering on minority carrier transport in bipolar transistors

Abstract We have examined the role of constraints on carrier flow on electron-hole scattering of minority carriers. In a bipolar transistor, in which the flow of majority carrier current normal to the junction potential barriers is usually negligible, the effect of electron-hole scattering is less than would be inferred from measurements of transport in p-i-n diodes or in the Shockley-Haynes experiment. In addition, as a result of the momentum transferred fromthe minority carriers to the majority carriers, an electric field is developed which enhances the flow of minority carriers, particularly at high injection levels.

Minority carrier injection and storage into a heavily doped emitter: Approximate solution for auger recombination

Abstract An analytic solution for the injected carrier distribution in a linearly graded, heavily doped region is given in terms of Hermite polynomials. The properties of this distribution are compared with those for the more usual diffusion length solution. An expression is given for the effect on high frequency response of the stored charge in the emitter region of a bipolar transistor.

ON A CURRENT INSTABILITY RESULTING FROM THE DIFFUSION OF HOT ELECTRONS

An instability of the electron concentration is predicted in a semiconductor with a nearly saturating drift velocity and a diffusion constant which increases with increasing electric field. A small signal analysis shows under what conditions fluctuations of the carrier concentration will be unstable.

Magneto-optic studies of the continuous-sheet memory

Abstract A number of continuous-sheet memory cells have been studied magneto-optically by means of the Faraday rotation in the Ce(PO 3 ) 3 glass. The data have been correlated with the results of simultaneous electrical measurements. Near the storage threshold, the observed storage of these cells is similar to that of an isothermal Crowe cell. When the cells are operated with larger drive currents, deviations from the simple isothermal Crowe-cell model are noted. These deviations are interpreted in terms of the spreading of the trapped flux in the continuous-sheet cell and in terms of heating.

On the additivity of ohmic and space charge limited currents

Abstract The current density is calculated for the case where both ohmic and space charge limited (SCL) contributions are important. It is shown that, although the actual current is less than the sum of the currents which would be obtained individually from the ohmic or SCL conduction mechanisms, the error involved in assuming their additivity is not large.