K. F. Yarn

Negative differential resistance of a delta-doping-induced double-barrier quantum-well diode at room temperature

A resonant-tunneling homojunction diode, which is a delta-doping-induced double-barrier quantum-well (D/sup 3/BQW) diode, is presented. The barrier uses the delta n/sup +/-i- delta p/sup +/-i- delta n/sup +/ structure. The current-voltage characteristics exhibit three sections of negative differential resistance (NDR) phenomena. At low bias, N-type NDR is demonstrated due to the resonant-tunneling effect. At higher bias, another N-type NDR appears due to the heating effect in the high electric field. As the external bias increases further, an S-type NDR is observed. This result is attributed to the impact ionization effect of thermionic electrons, and then trapping of holes in the maxima of the valence bands, resulting in barrier lowering and redistribution of voltage.<<ETX>>

Current-injection three-terminal GaAs regenerative switches

Gallium arsenide p+ –n−–δ(p+)–n−– n+ regenerative switches prepared by molecular beam epitaxy are demonstrated. Initially, their operation as an optical switch is considered. The position of a third-electrode (gate) profoundly influences the switching behaviours. Current-injection mode is then discussed. Silicon controlled rectifier (SCR)-like switches can be obtained. Comparisions are made by defining the control efficiency.

CHARACTERIZATION OF A GAAS CURRENT-CONTROLLED BIPOLAR-UNIPOLAR TRANSITION NEGATIVE DIFFERENTIAL RESISTANCE TRANSISTOR

GaAs current‐controlled bipolar‐unipolar transition negative differential resistance (NDR) transistors using an n+‐i‐p+‐i‐n+ homojunction structure prepared by molecular beam epitaxy are demonstrated. For a base thickness of 200 A and using a highly doped sheet concentration of 1013 cm−2, a NDR region is revealed for IB =100 μA, the proposed device operates as a conventional bipolar transistor. Additionally, the effects of base thickness on current‐voltage characteristics are also investigated.

Investigation of three-terminal voltage-controlled switching devices prepared by molecular beam epitaxy

Three-terminal GaAs switching devices prepared by molecular beam epitaxy using p+-n−-δ(p+)-n−-n+ structures are fabricated. The effects of the third-electrode position and the possible voltage-controlled operation on the device performance are discussed. Concepts are proposed to obtain new and improved voltage-controlled properties. The internal barrier of one proposed structure can be modulated directly and is found to be effective for the studied structures. The position of the third-electrode is found to affect the electrical properties profoundly due to different dominant mechanisms. Comparisions are made by defining a control efficiency. Due to the idea of varying the gate position, a conceptual understanding of such a set of results would enhance our understanding of the physics of bulk barrier devices in general.

A NOVEL GAAS CURRENT-CONTROLLED BIPOLAR UNIPOLAR TRANSITION NEGATIVE DIFFERENTIAL RESISTANCE TRANSISTOR PREPARED BY MOLECULAR-BEAM EPITAXY

Abstract GaAs current-controlled bipolar-unipolar transition negative differential resistance (NDR) transistors using n+-i-p+-i-n+ structure prepared by molecular-beam epitaxy (MBE) are demonstrated. Using a base thickness of 200 A and a highly doped sheet concentration of 1013 cm−2, a NDR phenomenon is revealed at base low injection level. The peak-to-valley current ratios are about eight at room temperature. This is proposed to be due to the bipolar-unipolar transition reaction. When the base is under a high injection level, the proposed device operates just like a conventional bipolar transistor. A hypothetical model is used and confirmed by experiments.

ROOM-TEMPERATURE OPERATION OF A NOVEL NEGATIVE DIFFERENTIAL RESISTANCE DEVICE PREPARED BY MOLECULAR-BEAM EPITAXY

Abstract A new negative differential resistance (NDR) device with a bulk barrier and resonant tunnelling structure has been prepared by molecular-beam epitaxy. A peak-to-valley current ratio up to 22 and a peak current density of 10 kA cm−2 are obtained at room temperature. The former is the largest value ever reported in the A1GaAs/GaAs system. Higher power output also can be expected.

Novel GaAs current-injection negative differential resistance transistor

GaAs current-injection negative differential resistance transistors using n+-i-p+-i-n+ structure prepared by molecular beam epitaxy are presented. For p+ with a sheet concentration of 1013 cm−2, a negative differential resistance region is revealed for a base currentIB<100 µA. The peak to valley current ratios are about 8 at room temperature. This is proposed to be due to the bipolar-unipolar transition reaction. WhenIB>=100 µA, the proposed device operates as a conventional bipolar transistor.

A Tristate Switch Using Triangular Barriers

We demonstrate a new GaAs regenerative switching device with a double triangular barrier (DTB) structure, i.e., p+-i- δ(n+)-i- δ(p+)-i-n+, prepared by molecular beam epitaxy (MBE). Using the concept of sequential collapse of the internal barriers, two distinctive switching regions are established. First, a negative resistance region (S-type) is observed, followed by a positive resistance region (inverted N-shape) in between the switching behavior with the increase of applied bias. This device may have applicability for tristate logic circuits.