Application of GaInP/GaAs DHBTs to power amplifiers for wireless communications

An InGaAs/GaAsP strain-compensated layer has been proposed as a base material for GaAs-based double heterojunction bipolar transistors (DHBTs). As known, decreasing bandgap energy of the base layer in heterojunction bipolar transistors (HBTs) can result in a smaller turn-on voltage. Using InGaAs as a base material is one possible approach to achieve the aim. However, compressive strain induced by InGaAs diminishes the influence of indium-adding-induced bandgap energy reduction, and thus abates the advantage of turn-on voltage reduction. In this study, a 280 Å GaAs 0.81 P 0.19 layer has been inserted below the In 0.054 Ga 0.946 As base layer to compensate the compressive strain induced by the InGaAs base layer. The result shows that the utilization of an InGaAs/GaAsP strain-compensated layer results in a reduction of the turn-on voltage by 20 mV. A turn-on voltage reduction of 190 mV over a conventional HBT with a GaAs base layer is achieved by utilizing the In 0.054 Ga 0.946 As/GaAs 0.81 P 0.19 strain-compensated base layer. This particular DHBT has a small offset voltage of 55 mV and a knee voltage of 0.6 V. A peak current gain of 58.98, a unity-current-gain cut-off frequency f T of 22 GHz and a unilateral power gain cut-off frequency f MAX of 25 GHz are also achieved for this particular DHBT.

Section: Resultsmentioning

confidence: 90%

Device characteristics of GaAs-based heterojunction bipolar transistors using an InGaAs/GaAsP strain-compensated layer as a base material

Wu¹,

Su²,

Chang³

et al. 2004

“…And the improvement in J Kirk from HBT with a thin high-doping layer in the collector is obtained by comparing equations ( 5) and (1).…”

Section: Kirk Effect and Output Powermentioning

confidence: 99%

“…There are increasing demands for high linearity power amplifiers with high efficiency in modern communications [1,2]. The choice of devices to be used in microwave power amplifiers is determined by many requirements, including high power gain, high breakdown voltage, high output power, high efficiency, good linearity, ruggedness and low cost [3].…”

Section: Introductionmentioning

confidence: 99%

Enhancedf_Tand linearity performance of InGaP/GaAs HBTs using a non-uniform doping collector

Wang¹,

Hsin²

2007

In this paper, the ac and power linearity characteristics of InGaP/GaAs heterojunction bipolar transistors (HBTs) with collector doping design have been presented. The collector design is to employ a thin high-doping layer inside the low-doping collector. The thickness, doping and location of the inserted layer are systematically studied with consideration of breakdown characteristics and the Kirk effect. The Kirk effect is relieved by redistributed electric fields in the non-uniform doping collector to extend the operational current and thus to increase the cutoff frequency ( f T ) and output power (P out ). The collector current at the onset of the Kirk effect is extended from 9.6 to 17.3 mA and f T is increased from 36 to 48 GHz for a device size of 4 × 12 × 2 µm 2 . The corresponding improvement in the saturation output power is 2.2 dB measured at 1.8 GHz. In addition, the impact of the collector doping profile on the base-collector capacitance (C BC ) and thus the linearity is simulated, discussed and measured. For an HBT with a thin high-doping layer being inserted 4000 Å from the base-collector junction, the experimental result on output third-order intercept point (OIP3) demonstrates the significant improvement by as large as 10 dB at a frequency of 1.8 GHz.

“…where q is the electron charge, ε is the permittivity of the collector material, N C is the constant collector doping density and n is the mobile electron density. As the collector current density, J C , and hence n in the n-p-n DHBT increases, the electric field profile is modified according to equation (1). When the electric field at that junction reaches zero this marks the onset of the Kirk effect [11].…”

Section: Analytical Modelmentioning

confidence: 99%

“…Double heterojunction bipolar transistors (DHBTs) incorporating wide bandgap semiconductors at both the emitter and the collector are actively being pursued for high power and high frequency applications. With collector thicknesses being reduced to achieve high-speed operation, the use of DHBTs with their wide bandgap collector is important to maintain high breakdown voltages [1]. Si/SiGe with its process compatibility with Si technology [2,3], GaInP/GaAs with its unique material and fabrication advantages over more conventional AlGaAs/GaAs [1] and InP/GaAsSb with its staggered type II band line-up [4] are all promising material systems for DHBTs that have shown excellent gain and frequency performances.…”

Section: Introductionmentioning

confidence: 99%

High current effects in double heterojunction bipolar transistors

Yee¹,

Houston²

2005

At high current densities, the onset of the Kirk effect is often the main frequency and power constraint in bipolar transistors. In this paper, we present an analytical model that accurately describes the physics behind the parasitic electron barrier formation in double heterojunction bipolar transistors in the Si/SiGe, GaInP/GaAs and InP/GaAsSb material systems at the onset of the Kirk effect. The model is tested by comparison with observations on GaInP/GaAs-based devices. A new lateral current spreading effect due to the electron barrier dependence on collector current density is also discussed.