Physics 610/Chemistry 678 Summer 2014 Problem Set #3 Due Monday, July 21st (1) Assuming that a 10 kg pure Si charge (i.e. melt amount) is used, what is the amount of boron that must be added to get the B-­‐doped Si to have a resistivity of 0.01 Ω-­‐cm when one half of the ingot is grown? (2) Refer to the phase diagram for GaAs found below. You are performing a liquid phase epitaxy* growth process. a. You add 100 g Ga metal to a carbon graphite boat with 10 atomic percent As and heat it until it is liquid. (i) How much As did you add? (i) What temperature does liquid start to form? (iii)What temperature is the whole mixture liquid? b. You stop heating when the sample is at 1000 ºC and quickly slide the hot graphite boat over a single-­‐crystal GaAs wafer that serves as an epitaxial growth template and cool the liquid to 600 ºC quickly so none of the GaAs wafer dissolves. (i) What mass of GaAs is deposited on the wafer? (ii) How thick is the film if you are using a standard 2” GaAs wafer as a growth template? * Epitaxy is where the GaAs single crystal simple gets bigger instead of nucleating crystals in solution; we’ll discuss later in more detail. (3) Explain why GaAs becomes Ga-­‐rich when heated. (4) A p-­‐type <100>-­‐oriented Si wafer with a resistivity of 10 Ω-­‐cm is placed in a wet oxidation system to grow a field oxide of 450 nm at 1050°C. Determine the time required to grow the oxide.