An exploration of avalanche effects of new RF and sub-millimeter wave semiconductor devices

The utilization of the avalanche multiplication effects for two novel RF sub-millimeter wave semiconductor devices is proposed: PN junction inductor and avalanche-assisted BIPOLITT diode. Small signal theoretical analysis and computer simulated results using a two-dimensional finite element simulation code were conducted on these two new device designs.;The new RF reverse-biased silicon PN junction inductor has a thin intrinsic region, which minimizes the space charge resistance associated with avalanche inductance. This is achieved by reducing the drift region in the device structure. It is also shown that if the intrinsic region width is extended without introducing an unwanted drift region, an intrinsic avalanche negative resistance can be generated to further reduce the total ohmic loss of the device. The inductance can be designed between 1 nH and 70 nH. The average quality factor, Q can be achieved around 200 by employing conservative specific contact resistance. At the same device, the maximum simulated quality factor, Q peak can be obtained over 1000 within the numerical limitation. Noise study of the proposed PN junction inductor was also conducted. The avalanche shot noise is estimated and can be optimized by implementing a longer intrinsic width, operating at a higher frequency and mixing with tunneling mechanism. In an LC oscillator circuit example, application of the proposed PN junction inductor with intrinsic width of 100 nm at 10 GHz operation yielded an estimated circuit phase noise of -110 dBc/Hz at the offset frequency of 1MHz with the Q value of 200. This suggests that the present novel PN junction inductor design can potentially be used in non-noise essential circuit applications.;The new sub-millimeter wave avalanche-assisted BIPOLITT diode is based on the HBT structure. This transit time device is operated with the base RF open. A high collector voltage is used to initiate the impact ionization at the base/collector junction. A large AC emitter junction current is achieved by the positive feedback at the base/emitter junction when excess avalanche carriers generated base/collector junction travels back to the base region. In one of our device design examples at 300 GHz, the simulated negative resistance was estimated to be about -10-6 O·cm 2 with DC current density of 105 A/cm2. The large negative resistance can potentially reduced the undesirable high frequency parasitic resistance and simplify the design complexity of sub-millimeter wave circuits.