tailieunhanh - Materials Science and Engineering - Electronic and Mechanical Properties of Materials Part 6

Tham khảo tài liệu 'materials science and engineering - electronic and mechanical properties of materials part 6', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Use of Minority Carrier Diffusion Equations Example Light shining on a surface of a semiconductor 0 hv G at x 0 assume infinite absorption coefficient to simplify example d 2 Ap Ap dX 1 DhT h x n-type Ap X Steady state solution d2 Ap Ap D 1 r------- G 0 in bulk h ỔX2 T h try Ap AeaX Be Now use boundary conditions of the problem @ X TO Ap 0 . A 0 AeaX BeaX a 2 Aea a2 Be- X Be X Ap Be D h a . VDhT h @ X 0 Ap Gt h . B Gt h Ap X Ap Gt h e Lh Units of length minority carrier diffusion length Lh J h eDh dp 1 e E. Fitzgerald-1999 7 Semiconductor Electronics Single crystalline - largely Si some III - V compounds Dominated by many nearly identical highly engineered junctions DRAMS today - 109 transistors Microprocessors 2002 - 108 transistors Total - 1018 yr - 106 person day e . Tuller 2001 8 4 5 Drift and Diffusion Holes diffuse 111 Electrons diffuse An electric field forms due to the fixed nuclei in the lattice from the dopants Therefore a steady-state balance is achieved where diffusive flux of the carriers is balanced by the drift flux E. Fitzgerald-1999 12