4. A silicon step junction with an area of 10-4cm2is doped NA=5x1015/cm3and ND=1015/cm3. Let ni=1010/cm3, kT=0.026 eV, DN=33.75 cm2/s, and DP=12.4cm2/s. If τP=0.4 µs and τN=0.1 µs, calculate: (a) generation rate in W; (b) generation current when VA= -0.1 and -10 volts; (c) the ratio IR-G/I0at VA= -10 V; (d) recombination current at VA=0.1 V and the ration of IRec/Idiffusion; (e) the value of VAwhere half the current is recombination and half is diffusion. 5. An ideal metal-semiconductor contact is made of a metal that has ΦM=4.75 eV, and a semiconductor that has χ=4.00 eV with ni=1010/cm3, ND=1016/cm3, and EG=1.00 eV; kT=0.026 eV.
University of Pennsylvania ESE 521 Semiconductor Device Physics and Technology Due: March 27, 2019 Prof. C. R. Kagan (a) Calculate the barrier for electrons in the metal. (b) Calculate Vbi, the barrier for electrons in the semiconductor. (c) Calculate the value of the depletion region width at thermal equilibrium. (d) Calculate the maximum electric field. (e) Sketch the energy band diagram in thermal equilibrium. 6. Heterojunctions: Draw the energy band diagrams, including vacuum levels, for Al0.2Ga0.8As-GaAs heterojunctions with the doping levels below. For each case give quantitatively the values for ∆Ec, ∆Ev, ΦAlGaAs, and ΦGaAs,and label them on your energy diagrams. Hint: remember what you need to calculate the workfunctions. (a) i-Al0.2Ga0.8As/i-GaAs (i is intrinsic) (b)p-Al0.2Ga0.8As/n-GaAs where NAin Al0.3Ga0.7As is 5x1015/cmwhere ND in GaAs is 5x1015/cm(c) p-Al0.2Ga0.8As/p-GaAs where NA in Al0.2Ga0.8As and GaAs is 5x1015/cmGaAs Eg 1.42 eV ε 12.9 ni= 2.1x106/cm3 χ= 4.07eV Al0.2Ga0.8As E1.67 eV ε 12.3 ni= 2.1x104/cm3 χ= 3.85 eV 33 3g