Processing math: 100%

PHT.301 Physics of Semiconductor Devices

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Electrons in crystals

Intrinsic Semiconductors

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pn junctions

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Schottky diode IV characteristics

A Schottky contact is formed when a metal is deposited on a semiconductor. The current-voltage characteristic of a Schottky diode has the same form as that for a pn-diode,

I=IS(exp(eVηkBT)1)[A].

Here I is the current, IS is the saturation current, e is the charge of an electron, V is the voltage, kB is Boltzmann's constant, T is the absolute temperature, and η is the nonideality factor where typically η=1 for a Schottky diode. It is sometimes said that a Schottky diode turns on at a lower voltage than a pn-diode, but the equation for the two types of diodes is the same. The difference is that Schottky diodes typically have a much larger saturation current IS so the current of a Schottky diode is much larger for the same voltage. For a real diode there is always a resistance RS in series. This modifies the diode equation to,

I=IS(exp(e(VIRS)ηkBT)1)[A].

This complicates the calculation since I now appears on both sides of the equation. However, such equations can be solved numerically, for instance by using a binary search. For a Schottky diode, the saturation current can be written as,

IS=Aemk2B2π23T2exp(ϕbkBT).

Here A is the area of the Schottky diode perpendicular to the current flow, m is the effective mass, ϕb is the energy between the Fermi energy of the metal and the conduction band of the semiconductor at the interface called the Schottky barrier height and T the temperature.

log10(I) [A]
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
0
-7
-6
-5
-4
-3
-2
-1

V [V]

A=

cm2

m

me

ϕb

eV

 

T=

K

Vmax=

V

η=

RS=

Ω

 


IS= 8.83e-7 [A];

V [V] I [A]
I [A]
-1.0
-0.5
0.0
0.5
1.0
-0.1
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7

V [V]