Nanoelectronics

1. Nanoelectronics Intro to Nanotechnology

2. Nanoelectronics • Introduction to Nanoelectronics • Electronics and Nanoelectronics • Microelectronics • Nanoscale Electronics • Nanoelectronic Devices

3. นาโนอิเล็กทรอนิกส์ เป็นองค์ความรู้ใหม่ที่ใช้ในการควบคุมอิเล็กตรอนที่อยู่ในอะตอม เรากำลังใช้อะตอมให้เป็นประโยชน์

4. นาโนอิเล็กทรอนิกส์ เป็นการประยุกต์ใช้นาโนเทคโนโลยีศาสตร์ด้านนาโนอิเล็กทรอนิกส์ เพื่อทำให้ผลิตภัณฑ์มีคุณภาพและทำงานด้วยประสิทธิภาพที่สูง ตัวอย่างเช่น การพัฒนาระบบไฟฟ้าเครื่องกลซูปเปอร์จิ๋ว การผลิตเซลส์แสงอาทิตย์ การพัฒนานาโนชิป ทำให้คอมพิวเตอร์ทำงานได้รวดเร็วและมีประสิทธิภาพสูง การพัฒนา High density probe storage device เป็นต้น

7. http://www.nanoworld.org/NanoLibrary/brief.pdf

9. “จำนวนทรานซิสเตอร์บนแผงวงจรรวมจะมีจำนวนมากขึ้นเป็นสองเท่าทุก 18 เดือน”

22. Electronics and Nanoelectronics Basic electronic definitions and relations

23. Electronic materials

25. Microelectronics • Introduction to band structure • Basic conductor and semiconductor physics • Transistors

26. Brillouin zone Crystal structure Band structure

27. direct band gap Indirect band gap

29. Fermi level falls inside the energy band. Easy for electrons to move around Fermi level falls between bands, with a large band gap. SiO2: 9 eV.>5eV Fermi level falls between bands, with a small band gap.Si: 1.11 eV, Ge:0.67 eV, GaAs: 1.43

30. Fermi-level positioning and carrier distributions

31. Density of states • There are 4 states per atom or 4 51022 / cm3 states in each of conduction and valence bands of Si. • The distribution of these states in the bands are not uniform, but follows a distribution function given by the following equations.

32. Fermi-Dirac distribution and the Fermi-level Density of states tells us how many states exist at a given energy E. The Fermi function f(E) specifies how many of the existing states at the energy E will be filled with electrons. The function f(E) specifies, under equilibrium conditions, the probability that an available state at an energy E will be occupied by an electron. It is a probability distribution function. EF = Fermi energy or Fermi level k = Boltzmann constant = 1.38 1023 J/K = 8.6  105eV/K T = absolute temperature in K

33. Fermi-Dirac distribution: ConsiderT > 0 K For E > EF : For E < EF : E EF 0 1 f(E)

34. Temperature dependence of Fermi-Dirac distribution

35. Exercise

36. Example Assume that the density of states is the same in the conduction band (CB) and valence band (VB). Then, the probability that a state is filled at the conduction band edge (EC) is equal to the probability that a state is empty at the valence band edge. Where is the Fermi level located? This corresponds to intrinsic material, where the # of electrons at EC = # of holes (empty states) at EV. Note that the probability within the band gap is finite, but there are no states available, so electrons cannot be found there.

37. Equilibrium distribution of carriers Distribution of carriers = DOS probability of occupancy = g(E) f(E) (where DOS = Density of states) Total number of electrons in CB (conduction band) = Total number of holes in VB (valence band) =

38. Fermi-level positioning and carrier distributions

39. Visualization of carrier distribution • One way to convey the carrier distribution is to draw the following diagram. This diagram represents n-type material since there are more electrons than holes.

40. Visualization of carrier distribution (continued) Another more useful way to convey the carrier distribution is to draw the following band diagrams. The position of EF with respect to Ei is used to indicate whether is n-type, p-type or intrinsic.

42. Semiconductor materials

44. Extrinsic semiconductors

45. PN junction depletion region

47. Total currents(PN junction) diffusion drift The total current flowing in semiconductor is given by: J = Jn + Jp

48. Drift current Drift current is the current flowing within a semiconductor as a result of carrier drift. By definition, I (current) =the charge per unit time crossing an arbitrarily chosen plane of observation oriented normal to the direction of current flow. = Q / t Ampere = Coulomb / second J (current density) = current per unit area = I / A

49. Drift current Consider a p-type semiconductor:

50. qpvdA is the “charge crossing the plane per unit time” and by definition is the “hole drift current”, Idrift By inspection, the current density associated with hole drift is Jp | drift = q pvd Since drift current arises in response toE-field, we need to find the relationship between drift current and E-field. At low electric field, it is found that drift velocity is proportional to E-field. Jp | drift = q pp E where p is the proportionality constant (called hole mobility)