Chapter 5. pn Junction Electrostatics Preliminaries Quantitative Electrostatic Relationships
※Doping profile : ND - NA 5. pn Junction Electrostatics pn junction ※Doping profile : ND - NA
◆ Step junction & Linearly graded junction 5. pn Junction Electrostatics ◆ Step junction & Linearly graded junction
◆ Contact Potential (Built-in Potential) : Vo or Vbi 5. pn Junction Electrostatics ◆ Contact Potential (Built-in Potential) : Vo or Vbi
5. pn Junction Electrostatics
◆ Poisson's Equation *charge density – in the case of fully ionized 5. pn Junction Electrostatics ◆ Poisson's Equation *charge density – in the case of fully ionized
5. pn Junction Electrostatics Integrating At equilibrium, (2)→(1)
5. pn Junction Electrostatics
Quantitative Electrostatic Relationships 5. pn Junction Electrostatics Quantitative Electrostatic Relationships ◆ Assumptions/Definitions
◆ Step Junction with VA = 0 5. pn Junction Electrostatics ◆ Step Junction with VA = 0 E = 0 outside of the depletion region p- side of depletion region
n-side of depletion region 5. pn Junction Electrostatics n-side of depletion region
p- side of depletion region 5. pn Junction Electrostatics p- side of depletion region n- side of depletion region
from : depletion region, space charge region 5. pn Junction Electrostatics from : depletion region, space charge region : charge neutrality within the depletion region
5. pn Junction Electrostatics (4), (5) → (3)
5. pn Junction Electrostatics
5. pn Junction Electrostatics
5. pn Junction Electrostatics
Total current diffusion + drift V < 0 5. pn Junction Electrostatics Total current diffusion + drift V < 0 I(gen.) due to EHP generation or minority carriers V = 0 V > 0 where I0 : I(gen.) - I0 : reverse saturation current (4) current flows : in the forward direction no current flows : in the reverse direction
◆ Step Junction with VA≠0 5. pn Junction Electrostatics ◆ Step Junction with VA≠0 - Applied Voltage bias VA across the transition region(W) of the junction - Change electrostatic potential barrier - Change the electric field in the transition region - Separation of the energy band - Change the width of the depletion region
5. pn Junction Electrostatics
5. pn Junction Electrostatics