ECE 874 Physical Electronics Prof Virginia Ayres Electrical

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, ECE 874, F 12

baseline situation W VM Ayres, ECE 874, F 12

Reverse biassed pn junction: l Ideally in depletion region W: p = n = 0 l (always do have thermally generated ni/pi but internal field E in W continuously sweeps them out) VM Ayres, ECE 874, F 12

New stuff in the picture: the effect of light VM Ayres, ECE 874, F 12

Effect of shining light on reverse biassed pn junction: l l l In depletion region W: p = n ≠ 0 In depletion region W: p = n = large In depletion region W: VM Ayres, ECE 874, F 12

xpp VM Ayres, ECE 874, F 12

VM Ayres, ECE 874, F 12

VM Ayres, ECE 874, F 12

VM Ayres, ECE 874, F 12

Lecture 26, 27 Nov 12 Chp. 06: Currents VM Ayres, ECE 874, F 12

General assuming capture/emission coefficients don’t change much from equilibrium values: Steady state: (5. 24) Equilibrium: 0 VM Ayres, ECE 874, F 12

Now include the ordinary mechanisms that can change n and p: drift currents and diffusion currents And anything else! drift diffusion VM Ayres, ECE 874, F 12

Now include the ordinary mechanisms that can change n and p: drift currents and diffusion currents And anything else! VM Ayres, ECE 874, F 12

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, ECE 874, F 12

Hw 06 Prs. 6. 3 and 6. 4: Diffusion: diff A diffusion current happens anytime you have a spatial variation in the concentrations of n or p VM Ayres, ECE 874, F 12

Example problem: from Pr. 6. 4: Put a red box around any region where ntype ness changes: dn/dx Put a blue box around any region where ptype ness changes: dp/dx -L -L/2 0 L/2 L VM Ayres, ECE 874, F 12

Example problem: from Pr. 6. 4: Put a red box around any region where ntype ness changes: dn/dx Put a blue box around any region where ptype ness changes: dp/dx -L -L/2 0 L/2 L VM Ayres, ECE 874, F 12

Example problem: from Pr. 6. 4: hole -L -L/2 0 L/2 L VM Ayres, ECE 874, F 12

VM Ayres, ECE 874, F 12

VM Ayres, ECE 874, F 12