A hybrid model is developed to simulate electron transport through the emitter-base heterojunction and the base region of abrupt heterojunction bipolar transistors. The energy distribution of the injected electron flux through the emitter-base junction is calculated using a rigorous quantum-mechanical treatment of electron tunneling and thermionic emission across the spike at the emitter-base junction. The results are compared with those predicted by the conventional thermionic-field-emission model. For both models, the electron fluxes injected across the emitter-base junction are used as initial energy distributions in a regional Monte Carlo calculation to model electron transport through the base. The average base transit times are calculated using the impulse response technique as a function of the emitter-base voltage. The differences between the thermionic-field-emission model and the rigorous quantum-mechanical approaches to model electron transport through abrupt heterojunction bipolar transistors are pointed out.
The Low Frequency Noise (LFN) in MOSFETs is critical to Signal-to-Noise Ratio (SNR) demanding circuits. Buried Channel (BC) MOSFETs are commonly used as the source-follower transistors for CCDs and CMOS image sensors (CIS) for lower LFN. It is essential to understand the BC MOSFETs noise mechanism based on trap parameters with different transistor biasing conditions. In this paper, we have designed and fabricated deep BC MOSFETs in a CIS-compatible process with 5 V rating. The 1/f γ LFN is found due to non-uniform space and energy distributed oxide traps. To comprehensively explain the BC MOSFETs noise spectrum, we developed a LFN model based on the Shockley-Read-Hall (SRH) theory with WKB tunneling approximation. This is the first time that the 1/f γ LFN spectrum of BC MOSFET has been numerically analyzed and modeled. The Random Telegraph Signal (RTS) amplitudes of each oxide traps are extracted efficiently with an Impedance Field Method (IFM). Our new model counts the noise contribution from each discretized oxide trap in oxide mesh grids. Experiments verify that the new model matches well the noise power spectrum from 10 to 10k Hz with various gate biasing conditions from accumulation to weak inversion. INDEX TERMS Low frequency noise (LFN), buried channel (BC) MOSFET, oxide trap, random telegram signal (RTS), impedance field method (IFM).
A model to simulate electron transport through the base region of abrupt heterojunction bipolar transistors has been developed taking into account the finite probability for electrons in the base to tunnel through the emitter-base spike back into the emitter. The average base transit time is calculated as a function of the emitter-base voltage using the impulse response technique. For all biases, the average base transit time is found to be smaller than its value computed while neglecting the finite probability for electrons with energy below the emitter-base spike to tunnel back into the emitter. For the case of an AlGaAs/GaAs structure, the average base transit time is found to increase with the forward emitter-base voltage.
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