Browse Prior Art Database

Heterostructure Traveling Wave Transistor

IP.com Disclosure Number: IPCOM000034186D
Original Publication Date: 1989-Jan-01
Included in the Prior Art Database: 2005-Jan-27
Document File: 3 page(s) / 47K

Publishing Venue

IBM

Related People

Fang, FF: AUTHOR [+2]

Abstract

This article describes a high frequency device which can be used as an amplifier or an oscillator at frequencies up to 1 teraHertz. The device disclosed herein relies on an interdigitated periodic comb gate to modulate the carrier concentration of a two-dimensional electron gas which is closely coupled to a conducting layer. Fig. 1 is a cross-sectional side view of a representative structure and Fig. 2 is a top view. Layer A is a n+ gallium arsenide (GaAs) layer which can be used as a back gate. Layer B is a n- GaAs separated from the two-dimensional electron gas (2DEG) by approximately 50 nm of undoped GaAs. Layer C is the modulation-doped layer which produces the 2DEG. On the top of the structure is an interdigitated comb gate.

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Heterostructure Traveling Wave Transistor

This article describes a high frequency device which can be used as an amplifier or an oscillator at frequencies up to 1 teraHertz. The device disclosed herein relies on an interdigitated periodic comb gate to modulate the carrier concentration of a two-dimensional electron gas which is closely coupled to a conducting layer. Fig. 1 is a cross-sectional side view of a representative structure and Fig. 2 is a top view. Layer A is a n+ gallium arsenide (GaAs) layer which can be used as a back gate. Layer B is a n- GaAs separated from the two-dimensional electron gas (2DEG) by approximately 50 nm of undoped GaAs. Layer C is the modulation-doped layer which produces the 2DEG. On the top of the structure is an interdigitated comb gate. If an AC signal is applied to the two terminals (a and b) of the gate there will be a periodic variation in the carrier density of the 2DEG given by: n = m nm eim(wt+kx)

_ where m = 0,1,2,3... and k is the wave vector of the two traveling waves propagating in opposite directions. From the geometry of the gate

(Image Omitted)

k = 2f/g and the wave velocity is fg where g is the pitch of the periodic structure. There is a longitudinally polarized (parallel to the surface) standing wave associated with the AC excitation in this geometry. The carrier relaxation time is long compared with the transit time between the fingers of the interdigitated gate electrode. Under these conditions the carriers will tend to bunch spatially with the same periodicity as the gate.

With an electric field applied to contacts c and d, the bunched carriers in the n GaAs...