Question

An ideal metal-semiconductor (M-S) junction is formed on the n-type Si semiconductor that is uniformly doped with a donor impurity (phosphorus) concentration of 1016 cm. The metal work function is 4.5 eV, and the Si electron affinity is 4 eV. Assuming that this M-S junction is at 300K, give your best answers to the following questions. (50 points) (a) At thermal equilibrium, draw the energy band diagram including meaningful parameters (energy barriers, energy levels, depletion width, etc.). (b) Calculate the work function of the Si semiconductor. (c) Calculate the built-in voltage in the Si region. (d) Calculate the depletion width in the Si region. (e) Will this M-S junction be Ohmic-like or Schottky-like? Explain clearly why. (f) When a forward bias voltage of 0.1V is applied, draw the energy band diagram including meaningful parameters (energy barriers, energy levels, depletion width, etc.). (g) In (1) case, will this M-S junction be Ohmic-like or Schottky-like? Explain why. (h) When a reverse bias voltage of 3 V is applied, draw the energy band diagram including meaningful parameters (energy barriers, energy levels, depletion width, etc.). (i) In (h) case, will this M-S junction be Ohmic-like or Schottky-like? Explain why. () Define the specific contact resistance (Re), and also explain how to minimize the specific contact resistance of a typical M-S junction.

Answer 1

Solchon. - Given =) An ideal Hetal- Seniconductor (M-5) Junction on the n type is forhed si Sericondukor that is =) concentration of Lolo em 3 -) the metal work function is 4.sev =) the sl Electron are inity as 4. ev. =) Assuming that this Mos junction is at 30ook. a) draw the energy band diagrari including Meaningful para Meter's ro) Mike Energy barriers, Energy levels, depletion width, Etci =) Before the . to (Vaccum Energy level) ON=4 sev *3=42v sic - - ET EFZ - tv

2 -> the After Depleting width EF Alter 3 we need to calculate the work function of the su sera conductor. Assuming Eg = levehoor thesi) Woxx function ois Semiconduct our js = yg + (Ec-Ep.)' A exs (E-BP)+(EPFF)0 = 4 + 1/ Kiln ( Aloy ) = 4 + " ! -0.0259 In hero) sub above the value in 290 ll.sxio 65 = 4 203 ev

( we need to calculate the built in voltage in the si Jegon. . But it in potential = (Total Band bending) sub. the I Com-Ps) to above value in ega = 19 (4.5-4.203) CV (VO) 0.2970 d) we need calculate the depletion width on the sh region Length of depleiton geglon x2&si (Vo) » MB ليلة و Sub the give and find value in E90 2x 1.3X8.85X totxo.237 - 1-6 8 10 19 x lolt V 7.0686 X8-8SXIOTH

= 10977 * 1099 m sed = 197.7 am e this Mas Junction:- ثم مالح This is the schottery like H-s Junction as the semiconductos has a lower Ranction of the retal ( Øn>03) + with the Rosword boas voltage of o.lv, - ----- varvm Energy level Love - eva = 1197 ev 0:56V=B - C . , g) in (f) (ase. As the prisosi the diode is Schottley - like

h reverse blas voltage of 3v os applied, draw 0.Sev = 48 . Evet evr = 3.297 - - - - EF y in thy case Here the as om 20s, the diode s ohnic the Sped fue conlect le sistance (R), - the contact reststance =) It as is detind the of (RC) is the measure of the case with which of worent can be the flow across a Mas interface. Reis de contact . .dI Way to reduce Rc: O Red as barrier height - 214. as dopting density n .