From figure , hio sGao 5P 0. Surface recombination could be reduced by growing a lattice-matched layer with a larger band gap on the surface to keep generated carriers from the surface.
Additionally, a secondary cell with a smaller band gap could be placed below the primary cell to absorb light which passes through. For example, Si could be utilized below GaAs. A quaternary alloy allows adjustment of both bandgap, and therefore wavelength, and lattice constant for epitaxial growth on convenient substrates. E Photon h-c x iio 4. In In.
Density of states gives available states as a function of energy. Effective density of states maps to the values at the band edges making calculations of carrier concentrations easy. Question 8 a Does mobility have any meaning at very high field? No, drift velocity saturates and is no longer linearly dependent on electric field. Hall effect and resistivity measurements. Chapter 4 Self-Quiz Question 1 Consider a p-type semiconductor that has a bandgap of 1. Question 2 a What do we mean by "deep" versus "shallow" traps?
Which are more harmful for semiconductor devices and why? What is an example of a deep trap in Si? Shallow traps are near the band edge. Deep traps are near the midgap. Deep traps are more harmful because they increase the chances of leakage. Gold Au forms deep traps. Si; indirect band gap c Do absorption coefficients of photons increase or decrease with photon energy? The absorption coefficient is very low below the band gap energy, increases abruptly at Eg, and continues to increase slowly at higher energies as more possible transitions become available with higher density of state.
E F is flat in equilibrium. Is the field constant or position dependent? Note that the carrier concentration scale is logarithmic such that exponential variations in the carrier concentration with position appear as straight lines. Circulate the appropriate arrow in each case. What are they? Which one dominates in forward bias and why? Reverse bias? Depletion capacitance is due to stored depletion charge. Diffusion capacitance is due to stored mobile carriers.
Diffusion capacitance dominates in forward bias. Depletion capacitance dominates in reverse bias. How are they defined? Alternating current signals are typically smaller than direct current bias. Both the substrate and epitaxial layer have a cubic crystal structure in the unstrained state.
Also, qualitatively show a 2-D view of the crystal structure in relation to the band diagram. Epitaxial Film Substrate JfJ. Assume no interface traps. TI metal semiconductor vacuum level -F,s energy semiconductor A postition b Is this a Schottky contact or an ohmic contact?
Ohmic contact Chapter 6 Self-Quiz Question 1 Label the following MOS capacitor band diagrams as corresponding to accumulation, weak inversion, depletion, strong inversion, flatband or threshold. Use each possibility only once. An active device gives power gain.
The power comes from the direct current power supply. Which is preferable? A voltage controlled device has much higher input impedence than a current controlled device and is preferable because it consumes less power.
Question 3 For Parts a through c below, consider the following low-frequency gate capacitance per unit area vs. Same as above. SV Circle one choice below.
Circle one. What clearly physically unrealistic aspect of these MOSFET characteristics besides less than smooth curves should have drawn suspicion? Chapter 7 Self-Quiz Question 1 Consider the following bipolar junction transistor BJT circuit and somewhat idealized transistor characteristics where, in particular, the voltage drop across the forward biased base-emitter junction is assumed to be constant and equal to IV for simplicity.
Sketch in the Fermi level as a function of position. Qualitative accuracy is sufficient. Cincrease unchanged I decrease b base transport factor B? If we increase the base doping, qualitatively explain how the various components change. If base doping increases, the injected electrons lost to recombination and holes supplied by the base contact for recombination increase, the electrons reaching the reverse-biased collector junction decrease because of lower electron concentration in the base, the thermally generated electrons and holes decrease slightly, and the holes injected across the emitter junction is unchanged.
Question 5 Would decreasing the base doping of the BJT increase, decrease or leave essentially unchanged circle the correct answers : a emitter injection efficiency 7? Assume essentially all recombination is direct and results in light emission. The forward bias current consists of holes injected from a contact to the left and electrons injected from a contact to the right. William Stallings 1.
Morris Mano 1. David Irwin 0. Morris Mano 0. Michael F. Ashby 0. William Thomson 0. Gene Mathers 0. Jack C. McCormac 1. William T. Segui 0. Richard T. Evans 0. Bill W. Tillery 0. Giorgio Rizzoni 0. Khurmi 1. Streetman, B. Sanjay — 6th Edition.
Atoms and Electrons. Energy Bands and Charge Carriers in Semiconductors. Excess Carriers in Semiconductors. Field-Effect Transistors. Bipolar Junction Transistors. Optoelectronic Devices. Integrated Circuits. High-Frequency and High-Power Devices. Appendices I. Definitions of Commonly Used Symbols. Physical Constants and Conversion Factors.
Properties of Semiconductor Materials. Derivation of the Density of States in the Conduction Band. Derivation of Fermi-Dirac Statistics. Solid Solubilities of Impurities in Si. Diffusivities of Dopants in Si and SiO2. Electronic Devices — Thomas L. Floyd — 7th Edition. Kasap — 2nd Edition. Device Electronics for Integrated Circuits — R. Muller, T. Kamins — 3rd Edition. Boylestad — 9th Edition.
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