ECE 874: Physical Electronics Prof. Virginia Ayres Electrical & Computer Engineering Michigan State University ayresv@msu.edu

Lecture 26, 27 Nov 12 Chp. 05: Recombination-Generation Processes VM Ayres, ECE874, F12

baseline situation W VM Ayres, ECE874, F12

Reverse biassed pn junction: Ideally in depletion region W: p = n = 0 (always do have thermally generated ni/pi but internal field E in W continuously sweeps them out) VM Ayres, ECE874, F12

New stuff in the picture: the effect of light VM Ayres, ECE874, F12

Effect of shining light on reverse biassed pn junction: In depletion region W: p = n ≠ 0 In depletion region W: p = n = large In depletion region W: VM Ayres, ECE874, F12

xpp VM Ayres, ECE874, F12

VM Ayres, ECE874, F12

VM Ayres, ECE874, F12

VM Ayres, ECE874, F12

Lecture 26, 27 Nov 12 Chp. 06: Currents VM Ayres, ECE874, F12

General assuming capture/emission coefficients don’t change much from equilibrium values: Steady state: (5.24) Equilibrium: VM Ayres, ECE874, F12

Now include the ordinary mechanisms that can change n and p: drift currents and diffusion currents And anything else! drift diffusion VM Ayres, ECE874, F12

Now include the ordinary mechanisms that can change n and p: drift currents and diffusion currents And anything else! VM Ayres, ECE874, F12

Now include the ordinary mechanisms that can change n and p: drift currents and diffusion currents And anything else! 6.1: review of drift 6.2: review of diffusion 6.3: list of equations for dn/dt, dp/dt and J’s – no new material VM Ayres, ECE874, F12

Hw06 Prs. 6.3 and 6.4: Diffusion: diff diff A diffusion current happens anytime you have a spatial variation in the concentrations of n or p VM Ayres, ECE874, F12

Example problem: from Pr. 6.4: Put a red box around any region where n-type ness changes: dn/dx Put a blue box around any region where p-type ness changes: dp/dx -L -L/2 L/2 L VM Ayres, ECE874, F12

Example problem: from Pr. 6.4: Put a red box around any region where n-type ness changes: dn/dx Put a blue box around any region where p-type ness changes: dp/dx -L -L/2 L/2 L VM Ayres, ECE874, F12

Example problem: from Pr. 6.4: hole VM Ayres, ECE874, F12 -L -L/2 L/2 L

VM Ayres, ECE874, F12

VM Ayres, ECE874, F12