Temperature dependence of single-event transients in SiGe heterojunction bipolar transistors for cryogenic applications

We experimentally demonstrate that the dominant mechanism of single-event transients in silicon-germanium heterojunction bipolar transistors(SiGe HBTs)can change with decreasing temperature from+20℃to-180℃.This is accomplished by using a new well-designed cryogenic experimental system suitable for a pulsed-laser platform.Firstly,when the temperature drops from+20℃to-140℃,the increased carrier mobility drives a slight increase in transient amplitude.However,as the temperature decreases further below-140℃,the carrier freeze-out brings about an inflection point,which means the transient amplitude will decrease at cryogenic temperatures.To better understand this result,we analytically calculate the ionization rates of various dopants at different temperatures based on Altermatt's new incomplete ionization model.The parasitic resistivities with temperature on the charge-collection pathway are extracted by a two-dimensional(2D)TCAD process simulation.In addition,we investigate the impact of temperature on the novel electron-injection process from emitter to base under different bias conditions.The increase of the emitter-base junction's barrier height at low temperatures could suppress this electron-injection phenomenon.We have also optimized the built-in voltage equations of a high current compact model(HICUM)by introducing the impact of incomplete ionization.The present results and methods could provide a new reference for effective evaluation of single-event effects in bipolar transistors and circuits at cryogenic temperatures,and could provide a new evidence of the potential of SiGe technology in applications in extreme cryogenic environments.

GERO: a general SCA-based readout ASIC for micro-pattern gas detectors with configurable storage depth and on-chip digitizer

The paper presents GEneral ReadOut (GERO), a general readout ASIC based on a switched capacitor array for micro-pattern gas detectors. It aims at providing general readout electronics for low-to-medium event-rate gas detectors with high sampling frequency, configurable storage depth, and data digitalization. The first prototype GERO chip integrates 16 channels and was fabricated using a 0.18-lm CMOS process. Each channel consists of a sampling array working in a ping-pong mode, a storage array with a 1024-cell depth, and 32 Wilkinson analog-todigital converters. The detailed design and test results are presented in the paper.

Single event transient characterization of SiGe HBT by SPA experiment and 3-D process simulation

The single-photon absorption induced single event transient in the silicon-germanium heterojunction bipolar transistor is investigated.The laser wavelength and bias condition have been proven to have significant impacts on the characterization of the single event transient(SET) response of the device by two-dimensional(2-D) raster scanning.After optical analytical calculation,the laser-induced charge distribution is well-embedded in the 3-D TCAD process simulation conducted to explore the underlying physical mechanism.In addition to the ion shunt effect,the excess electron injection from the emitter to the base could play a vital role in the SET peak amplitude and charge collection.The impact of the metal layer on the SPA experimental results is also determined by establishing a figure of merit that will help researchers estimate the laser-induced transient sensitivity of devices with metal layer blocking.