P-type Ring Research Articles

Ultra-Low Capacitance Spot PIN Photodiodes

Spot PIN photodiodes were integrated without any process modifications in a high-voltage 0.18 μm CMOS technology. These photodiodes are a combination of vertical and lateral PIN photodiodes using the P+ bulk wafer and a P-type ring at the surface as anodes. Devices with N+ cathode and N+/N-well cathode are compared. A small N+/N-well cathode spot reduces the capacitance to 1.47 fF and the N+ cathode spot leads to a capacitance of 1.07 fF. The light sensitive area of these photodiodes is 707 μm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . Simulated electric field distributions show the full depletion of the spot PIN photodiodes. Responsivities from 0.12 A/W to 0.16 A/W and from 0.50 A/W to 0.52 A/W for 405 nm and 675 nm, respectively, are achieved. The measured bandwidths for 675 nm light are from 520 MHz to 690 MHz at reverse biases from 15 V to 30 V.

Classes of ring galaxies generated by dynamical friction

Dynamical friction is incorporated in the numerical modeling of colliding ring galaxies. We show that dynamical friction may lead to the capture of an initially unbound companion into a damped oscillatory orbit before ultimately merging with the target disk. In the late stages of its motion the companion may be virtually merged with the main galaxy while rings are still propagating in the disk. This raises the possibility that there exist (at least) two classes of ring galaxies: a class of ring galaxies with separate detached companions in which dynamical friction is too weak to have captured the collider, and a second class with no apparent companion in which the latter has either merged with the target galaxy or has disrupted. These two classes could possibly be identified with O-type and P-type ring galaxies of Few and Madore (1986).

Use of a surrounding p-type ring to decrease backgate biasing in GaAs MESFET's

The sensitivity to backgate biasing of two MESFET designs, one with an implanted surrounding p-ring and one without, were compared. A highly resistive p-like surface layer, possibly arising from the uncapped anneal, is thought to be the agent of the backgating. The addition of the surrounding p-ring results in greatly decreased backgate biasing.