Reduction of UHF power transistor distortion with a nonuniform collector doping profile

Abstract

Abstract-The linearity of a class-A, bipolar UHF power transistor is investigated. The device is intended for transmission of signals with multiple (TV) channels. Mixing between the various channels must be suppressed, which makes linearity an important parameter. This paper presents a novel approach, where process technology is specifically optimized to minimize distortion. It is shown that particularly the nonlinear collectorbase capacitance strongly affects the linearity of this type of device. With a modified collector-base doping profile, the capacitance is manipulated. A nonuniform profile is introduced that significantly reduces third-order intermodulation. The profile consists of an arsenic doped spike that is grown epitaxially into the (otherwise) lightly doped collector. This reduces the bias dependence of cb and improves the tradeoff between linearity and breakdown or ruggedness. The reduction in third-order intermodulation is demonstrated both experimentally and by mixed-level MDS/MAIDS simulations.

Controlled Growth of Non-Uniform Arsenic Profiles in Silicon Reduced-Pressure Chemical Vapor Deposition Epitaxial Layers

“…This has, in particular, been demonstrated for microwave and radio frequency (RF) applications. [1][2][3][4] However, it is often the doping fabrication technology that limits the range of devices that are feasible. Doping profiles of demanding shape cannot be achieved by ion implantation, and Si epitaxy remains the method of choice.…”

Versatile N-Type Profile Engineering by Controlling Arsenic Surface Segregation in Silicon RPCVD

“…Precise engineering of doping profiles can greatly improve the performance of Sibased devices, especially for microwave and RF applications. For example, in bipolar technology tailoring the collector with a non-uniform doping profile can enhance highfrequency behavior by, for example, improving the trade-off between linearity and ruggedness [1], or by increasing the maximum cutoff frequency f T [2]. Moreover, for varactor diode-based circuit topologies, which have recently been presented as high-Q "distortion-free" tunable capacitive elements for RF adaptivity [3], there is an increasing demand for a wider tuning range.…”