Aritra Acharyya

Dark current reduction in nano-avalanche photodiodes by incorporating multiple quantum barriers

ABSTRACT Multiple quantum barriers have been used to suppress the dark current of nanoscale avalanche photodiodes (APDs). The n+–π–p+-structured Si–3C-SiC heterojunction-based multiple quantum barrier (MQB) APDs are considered and a detailed model of dark current has been developed from the self-consistent solution of the coupled Schrödinger–Poisson equations. Four major types of electron–hole pair (EHP) generation mechanisms such as (1) thermal generation, (2) band-to-band tunnelling generation, (3) trap-assisted tunnelling generation and (4) avalanche generation are considered for calculating variation of the total dark current with reverse bias voltage. It is observed that the dark current can be suppressed significantly by increasing both the number and thickness of quantum barriers. However, the authors have also admitted that both the number and thickness of quantum barriers cannot be increased indefinitely, since it will cause deterioration in spectral response of the device in near-infrared range (λ < 1100 nm).

Influence of Carrier–Carrier Interactions on the Noise Performance of Millimeter-Wave IMPATTs

ABSTRACT The influence of inter-carrier scattering phenomena on the noise performance of double-drift region (DDR) impact avalanche transit time diodes has been investigated. Three optimized Si DDR diode structures operating at 94, 140 and 220 GHz have been taken into account for this study. A newly reported analytical model of the ionization rates has been incorporated in the simulation in order to consider the effect of inter-carrier scattering inside the active region of the diodes and the noise performance of those have been evaluated by calculating the noise spectral density and noise measure around respective operating frequency bands. Results show that the noise performances of those are drastically worsened due to the aforementioned effect. The said deterioration has been found to be monotonically increasing in nature with the working frequency.

Enhancement of avalanche noise in IMPATT diodes due to E-E and H-H collisions

The effect of energy-loss due to electron-electron (e-e) and hole-hole (h-h) collisions on the avalanche noise performance of IMPATT diodes has been studied. Simulations have been carried out on DDR Si IMPATTs operating at 94, 140 and 220 GHz. Simulation results show that the noise measure of the diodes considerably increases due to e-e and h-h interactions within the space charge layer of the device. This is observed to be more influential at higher mm-wave frequencies.

Avalanche noise in MQW DDR IMPATTs

The avalanche noise performance of multiple quantum well (MQW) DDR IMPATT devices has been investigated. A self-consistent quantum drift-diffusion (SCDD) model is used for the simulation study. The noise performance of one Si based flat and two Si∼3C-SiC MQW DDRs have been studied in this paper. Results indicate that considerable low noise operation with high power output can be obtained at W-band by using the Si∼3C-SiC MQW DDR structures.

Avalanche noise in magnetic field tunable avalanche transit time device

Influences of magnetic field on the noise performance of double-drift region (DDR) impact avalanche transit time (IMPATT) device based on Si designed to operate within W-band (75–110 GHz) have been studied in this paper. The reverse biased DDR IMPATT structure under transverse magnetic field can be regarded as magnetic field tunable avalanche transit time (MAGTATT) device. The simulation results show that both the noise spectral density and noise measure of the device increase significantly while the device is kept in transverse magnetic field. This degradation of the noise performance of the device enhances when the magnitude of the magnetic field is increased. Therefore, in order to achieve the magnetic field tuning of the RF properties of DDR IMPATTs as reported earlier by the authors, the noise performance of the source has to be sacrificed in fair extent.