Consider two gallium arsenide (????????, ???? = 12.9) pn junctions. They both have a p-type region with ???? = 5 1017 ???? 3 and an n-type region with ???? = 1019 ???? 3. The first device (we will call "step" junction) has these two regions in direct contact. The second device (we will call "p-i-n" junction) has an additional UID (unintentionally doped) region of width ???? = 100 ???? in between these two regions doped with ????,?? = 1016 ???? 3. (a) Find and sketch the charge density, built-in field and potential for each of these cases at zero bias. Indicate the length of each depletion region. (b) Compare the maximum field in the p-i-n diode to that in the step junction without the lightly doped n region, but with the same dopant concentrations in the other regions. Why are they different