NNSE618-L18-MS-junction

NNSE618-L18-MS-junction - 1 Lecture contents...

Info iconThis preview shows pages 1–6. Sign up to view the full content.

View Full Document Right Arrow Icon
NNSE 618 Lecture #18 1 Lecture contents Metal-semiconductor contact Electrostatics: Full depletion approximation Electrostatics: Exact electrostatic solution Current Methods for barrier measurement
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
NNSE 618 Lecture #18 2 metal-semiconductor contact p-n homojunctions heterojunctions Formalism includes the following phenomena: Statistics of carriers Continuity equations: Poisson equation (Gauss equation) in SI: Current equations Drift and diffusion currents Einstein relation (in non-degenerate semiconductor) Thermionic current Tunneling current Junctions: general q T k D B n T k nq J B n n n qD J n n n n n n J q R G t n 1 p p p J q R G t p 1 p J p p p  4 D 4 2 2 0 replace 0 cm F 14 0 10 85 . 8  => Formation of potential barriers. Different from bulk material
Background image of page 2
NNSE 618 Lecture #18 3 Formation of metal/semiconductor interface Band diagram before contact established Charge redistribution at contact Band diagram of M-S contact (Schottky) Barrier height Built-in potential From Van Zeghbroeck, 1996
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
NNSE 618 Lecture #18 4 Metal-semiconductor contact M-S contact properties are determined by potential (or field) variation in the semiconductor (not metal) Usually difference in work- functions does not determine the contact barrier due to existance of interface levels Interface states pin the Fermi level somewhere around mid– gap and the barrier height is thus virtually independent of the metal work function However, the basic formalism for currents is still valid M-S contact almost always contains depleted layer in the semiconductor From Sze, 1981 Contact formation with Fermi energy pinning at surface traps Barrier does not depend on work function of metal! Contact formation in ideal case (Schottky approach)
Background image of page 4
NNSE 618 Lecture #18 5 Metal-semiconductor contact In GaAs there is hardly a dependence of M-S contact barrier properties on metal Most of the barrier are within 0.2 eV though metal work functions are within 0.8 eV From Murakami, 1993 M-S barrier height of n-GaAs vs. work function of metal
Background image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 6
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 25

NNSE618-L18-MS-junction - 1 Lecture contents...

This preview shows document pages 1 - 6. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online