Patent ID: 6252250
Filing Date: 2001-06-26
Classification: H01L

Abstract:
A high power IMPATT (Impact Avalanche Transit Time) diode for generating high frequency signals having two electrodes, an anode (2) and a cathode (1), and a semi-conductor layer there between, with a pn-junction (8) for blocking conduction of the diode when a voltage is applied in a reverse direction across the electrodes,said semiconductor layer comprising a low doped n-type drift layer (7) between the junction (8) and a first (2) of said electrodes through which charge carriers are transported upon avalanche breakdown in the semiconductor layer and avalanche multiplication of charge carriers when a voltage high enough is applied across the electrodes in said reverse direction,characterized in that said semiconductor layer is provided with means (9) structured and arranged to locally increase the electrical field in the drift layer substantially with respect to the average electric field therein for generating said avalanche breakdown at a considerably lower voltage across said electrodes than if the doping of the active region of the diode were substantially constant across the entire active-region layer (7,9),said semiconductor is made of crystalline 4H SiC oriented such that the avalanche process occurs parallel to a principal axis (c-axis),said semiconductor layer contains a localized avalanche region structured and arranged such that the electric field therein is substantially higher than the average field in the region adjacent to the avalanche region, andsaid semiconductor layer is oriented with a current direction thereof substantially parallel to the principal axis of the crystal and to a plane of the substrate.