Question

Plot I-V characteristic of a p-n junction diode, and describe the phenomenon of avalanche breakdown phenomenon in a Schottky diode.

Answer 1

I-V characteristic of a p-n junction diode:

+In Forward (MA) Current - -V + +- Reverse voltage Forward voutage Germanium Silicon 10.3 10.1 Avalanche breakdown region -I & Reverse wrrent (MA)

Avalanche breakdown phenomenon in a Schottky diode:

The schottky diode is one of the diodes which have zero diffusion capacitance and smaller transition citance than normal diodes. The diode is formed by the junction between a metal and a semicono in which the work function of metal larger than semiconductor. Assuming the schottky diode across a supply Voltage, as load current or supply Voltage changes, the diode current will accomodate itself to these changes to maintain a nearly constant load voltage. The schottky diode will continue to regulate until the diode current fall to knee of diode Volt-ampere curve. r ole dinde breakdown for

diode Vocarpe Two mechanisms of diode breakdown for increasing revease Voltage are recognised. In one mechanism, the thermally generated electrons & holes acquire sufficient energy from the applied potential to produce new carriers by removing Valence electrons from their bonds. These new carriers in turn pro additional carrier again through process of disrupting bonde. This process is referred to as avalanche multiplication. It results in flow of large reverse currents and the diode find itself in region of avalanche break down. Even if the initially available cartiers do not acquire sufficient energy to disrupt bonds it is possible to initiate break down through a direct supture of bonds because of existence of strong electric field under these circumstances, the breakdown is referred as avalanche breakdown phenomenon.

borak down is du In general, schottky diode suffer from their very limited avalanche break down stability due to avalanche breakdown stability due to avalanche current filamentation at the schottky interface. The avalanche test is an essential reliability standard test for high power devices as this phenomenon man ha phenomenon may happen in every switching converter during transient operating modes: