The systems approach to training

A semiotic rebel:

Stephen Townes’ quilt art of a young Nat Turner provides a glimpse of Turner’s intelligence, humanity, and how love endured the horrors of enslavement.

Stamped From the Beginning suggests that even some famous Black leaders who fought for freedom exhibited ‘racist ideas about Black people’:

This book inspired a young Frederick Douglass:

Equiano’s experience on a slave ship introduced him to a type of slavery that seemed worse than other forms of slavery he had known:

Dr. Feimster suggests we need to ask ‘different questions’ to get a fuller understanding of what violence looked like during the Civil War:

Dr. Cornel West and Tavis Smiley both argue that Malcolm X demonstrated far more courage than Dr. King:  

Question 4: (25 points) For a silicon pn junction at 300 K with the following parameters: Na = Nd = 1×1015 cm–3, e = 1.60×10–19 C, ni = 1.5×1010 cm–3, Dn = 25 cm2/s, Dp = 10 cm2/s, and tpo = tno = 5×10–7 s. Determine: The total reverse saturation current density at 300 K. (5 points) The total reverse current is composed of the reverse current of electrons Jsn and that of holes Jsp. Determine the ratio of Jsn to Jsp, Jsn/Jsp. (6 points) All the parameters above are more difficult to control except the doping concentration. If you keep one doping concentration constant, say you keep Na constant at 1×1015 cm–3, what is the other doping concentration Nd to increase the Jsn/Jsp ratio to 3? (7 points) If you want to operate this pn junction at 400 K and keep the total reverse saturation current the same as in part (a), what would be the doping concentration if you also keep Na = Nd? ni = 2.38×1012 cm–3 at 400 K and all other parameters are independent of temperature. (7 points)

Question 1 (30 points) Gallium arsenide (GaAs) has a zincblende structure. Its lattice constant is 5.65 Å (1 Å = 1×10–8 cm). (a) How many arsenic atoms the unit cell below contains? Please show your calculation. How many gallium atoms does the unit cell contain? (8 points) (b) On its (100), what is the atomic density of arsenic atoms? That is, how many arsenic atoms are there on a 1-cm2 area? Show your procedure to obtain this number. The unit should be atoms/cm2. (7 points) (c) Determine the atomic density of gallium arsenide in atoms/cm3, that is, the total number of gallium and arsenic atoms in a 1-cm3 volume. (7 points) (d) If the atomic mass unit (AMU) of gallium and arsenic atoms are 69.7 and 74.9, respectively (1 AMU = 1.6605 × 10–24 grams), what is the density of gallium arsenide in grams/cm3. (8 points)