System Echo Growth Procedures

Growth Procedures for Echo

• Turn down HVP 200 C

• STO

  • Once STO finishes turn down BufferHTS to 10 C

  • Re-check fluxes before starting group-V fluxes. If too far off, re-adjust

  • Open new database file and enter in group-III fluxes, BF bckgrnd and HVP Power

• GroupV Flux mapping(As and Bi)

  • As-Flux mapping:

    • take up to high flux (200 or 250)

    • then take down to desired fluxes (can base this on past growths)

    • record fluxes in database and insert in recipe

    • NOTE: this is the old way of taking As fluxes

    • current standard practice (As of 2018)

    • We've moved to As STOS that map flux as a function of valve position (look in the log files for examples)

    • As STOS should be run low to high to avoid saturating the BF background with excess As

• RHEED ramp up

  • start EZ RHEED program

  • make sure both shutters are closed

  • turn on module (make sure both knobs are zeroed)

  • slowly turn up current to 2.63A

  • slowly turn up voltage ~1 kV/30 sec to 8 kV

  • check the anode current (want it to be 2-3 microA)

  • always open shutter in front of gun first, then in front of window

• Load Recipe

  • once groupV fluxes are done, load & compile (but don't run) recipe (unless need multiple sub temperatures)

  • close AsValve, close shutter

  • turn off beam flux gauge

• Loading wafers

  • if BufferHTS is <200 C & CAR is <250 C, unload baked wafer from HTS and load on a new wafer

  • (Manually) rotate CAR to transfer position (stop rotations first!)

  • make sure CAR is at optimal loading position: 180 degrees

  • put CAR heater in MANUAL mode so that it doesn't overpower, give it a couple % of power

  • GC transfer arm nosepiece clamp up & to the left for loading on trolley

  • GC transfer arm orientation with nosepiece clamp flat side down to load onto CAR

  • remove RHEED block and load to-be-grown wafer (update trolley sheet)

  • turn up BufferHTS to bake out next wafer

• Baking wafer away from SF

  • CAR in transfer position

  • switch Sub back to AUTO

  • bring wafer up to baking temperature (same a HTS temp)

  • bake for 10 min (once it reaches set temperature)

• DeOX of wafer

  • rotate wafer to GROWTH position (0.0)

  • over As shutter, set AsValve to 250 mil

  • begin rotations 5 rpm (CW)

  • check RHEED that wafer is amorphous

  • bring up substrate TC, watching the pyro for deox temperature

  • for GaAs, deox occurs at ~600C pyro (start TC ~600 until 800 by 50 and then up by 10 until ~860)

  • once you see the specular spot, set timer for 15 minutes

  • check RHEED after about 10 min to make sure streaky pattern appears

• Prep before recipe

  • set substrate temperatures (pyro) used during recipe

  • if using multiple temperatures, map out set and incorporate into the recipe

  • ~2C TC / ~1C pyro

• Start recipe

  • if recipe is waiting, click continue

  • watch RHEED when needed to check streakiness.

• For each growth

• for a re-growth:

  • if growing the wafer at same substrate temperature (pyro), use same recorded TC temperature (surface roughening makes it hard to get an accurate pyro reading)

• source cool down recipe is saved on growth computer folder "maintenance" recipes

• "Away bake"

  • GaAs (UID/SI): 450

  • n-/p-GaAs: 400

  • GaSb (UID): 350

  • n-GaSb : 300

  • InP : 400

  • GaP : 400

• "DeOx temperatures"

  • nGaAs ~800C TC

  • SI GaAs ~600 C pyro

  • nGaSb ~550 pyro

  • SI InP ~540 pyr0 (watch for the 4x and cool down immediately if using As to deox)

  • GaP ~650 pyro

-:(doped wafers reach pyro temperature at lower TC because the free carrier absorption is higher. GaSb exhibits similar behavior when compared to GaAs because it has a narrower bandgap.)