PVMD Ren van Swaaij Delft University of Technology Metal and - PowerPoint PPT Presentation

Metal-semiconductor junctions PVMD René van Swaaij Delft University of Technology

Metal and semiconductor band diagram E vac E vac q φ sem q φ m E F E F

Metal and semiconductor band diagram E vac E vac q φ sem q χ sem q φ m E F E F

Learning objectives • Make the junction between the metal and semiconductor • Schottky barrier junction • Ohmic junction

Forming the junction E vac E vac q φ sem q χ sem q φ m E F E F

Forming the junction E vac E vac q φ sem q χ sem q φ m E F q φ ms = q φ m - q φ sem E F

Forming the junction E vac q φ ms E vac q φ sem q χ sem q φ m E F E F

Forming the junction q φ ms E vac q φ sem q χ sem q φ m E F E F

Forming the junction E vac q χ sem q φ sem q χ sem q φ m E F E F

Forming the junction E vac q χ sem q φ sem q χ sem q φ m E F E F

Forming the junction E vac q χ sem q φ sem q χ sem q φ m q φ Bn E F E F

Forming the junction E vac q χ sem q φ sem q χ sem q φ m q φ Bn E F E F q φ n

Forming the junction q φ ms = qV bi = q ( φ Bn - φ n ) E vac q χ sem q φ sem q χ sem q φ m q φ Bn E F E F q φ n

Forming the junction x d q φ ms = qV bi = q ( φ Bn - φ n ) E vac q χ sem q φ sem q χ sem q φ m q φ Bn E F E F q φ n

ρ x d

ρ qN d x d

ρ qN d x d

ρ qN d x d Poisson equation

ρ qN d x d Poisson equation Gauss’s law

ρ qN d x d F

ρ qN d x d F Φ

Forming the junction x d q φ ms = qV bi = q ( φ Bn - φ n ) E vac q χ sem q φ sem q χ sem q φ m q φ Bn E F E F q φ n Φ

Depletion region width ρ qN d x d Poisson equation

Depletion region width ρ qN d x d Poisson equation Depletion region width

Forming the junction x d q φ ms = qV bi = e ( φ Bn - φ n ) E vac q χ sem q φ sem q χ sem q φ m q φ Bn E F E F q φ n

Schottky junction under forward bias q ( V bi - V a ) E vac q φ sem q χ sem q φ m E F E F

Schottky junction under forward bias q ( V bi - V a ) E vac q χ sem q φ sem q χ sem q φ m q φ Bn E F E F

Schottky junction under forward bias q ( V bi - V a ) E vac q χ sem q φ sem q χ sem q φ m q φ Bn E F E F

Schottky junction under forward bias q ( V bi - V a ) x d E vac q χ sem q φ sem q χ sem q φ m q φ Bn E F E F

ρ qN d x d

ρ qN d x d

Depletion region width ρ qN d x d Poisson equation Depletion region width

ρ qN d x d F Φ

Schottky junction under reverse bias q ( V bi + V R ) E vac q φ m q χ sem q φ sem E F E F

Schottky junction under reverse bias q ( V bi + V R ) E vac q χ sem q φ m q χ sem q φ sem q φ Bn E F E F

Schottky junction under reverse bias q ( V bi + V R ) E vac q χ sem q φ m q χ sem q φ sem q φ Bn E F E F

Schottky junction under reverse bias x d q ( V bi + V R ) E vac q χ sem q φ m q χ sem q φ sem q φ Bn E F E F

In case φ m is smaller than φ sem E vac E vac q φ sem q χ sem q φ m E F E F

In case φ m is smaller than φ sem E vac E vac q φ sem q χ sem q φ m E F E F

In case φ m is smaller than φ sem E vac q φ sem q χ sem q φ m E F E F

In case φ m is smaller than φ sem E vac q χ sem q φ sem q χ sem q φ m E F E F

In case φ m is smaller than φ sem E vac q χ sem q φ sem q χ sem q φ m E F E F

Conclusions • If work function n -type semiconductor is smaller than metal work function a Schottky barrier is obtained

Summary • If work function n -type semiconductor is smaller than metal work function a Schottky barrier is obtained • If work function n -type semiconductor is larger than metal work function an ohmic junction is obtained