System Bravo Growth Procedures

Turn down HVP to 30 (if growing cold)

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

RHEED ramp up:

start EZ RHEED program
turn on module (make sure both knobs are zeroed)
slowly turn up current 0.1 A/30 sec, pause at 1 A and then take it up to 1.35 A at 0.1A/30sec
slowly turn up voltage ~1 V/30 sec to (9 V GaSb, 10 V GaAs)
always open RHEED shutter first, then turn off beam blanking

GroupV Flux mapping:

when using Sb, always take Sb first
Sb has hysterisis: start at 0, go to high flux, then to 1st, 2nd etc fluxes in order.

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

Load Recipe:

once groupV fluxes are done, load recipe (unless need multiple sub temperatures)
close AsValve, close shutter
turn off beam flux gauge

Loading wafers:

if BufferHTS is <200 C, unload baked wafer and load on a new wafer
rotate CAR to transfer position (stop rotations first!)
make sure CAR is at optimal loading position: rotation angle = 0.0
put CAR heater in manual mode so that it doesn't overpower
GC transfer arm orientation with nosepiece clamp flat side down to load onto CAR
remove RHEED block and load to-be-grown wafer
turn up BufferHTS to bake out next wafer

Pyro set up:

As deox overpressure (AsValve = 250), sub @ 200C, shutter open!
with wafer in RHEED position, with 5 rpm rotation CCW, set pyro current offset to "0"
wait for pyro to stabilize and sample current offset, record in database

Baking wafer away from SF:

rotate wafer away from SF (STOP ROTATIONS FIRST)\
switch Sub back to AUTO
bring wafer up to baking temperature (same a HTS temp)
bake for 10 min

DeOX of wafer:

rotate wafer to RHEED position, begin rotations 5 rpm
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 700 by 50 and then up by 10 until ~740)
for GaSb deox occurs at ~550C pyro
once you see the specular spot, set 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: reset pyro current offset (record in database), set to "0" and then take offset (with wafer facing the SF) pyro growth temperatures for deox, and growth (record TC and pyro readings in database)

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:

saved on growth computer under Adam's folder in "maintenance" recipes

Away bake temperatures

GaAs (UID/SI): 450
n-/p-GaAs: 400
GaSb (UID): 350
n-GaSb: 300
InP (Fe doped, SI): N/A (Don't away bake)

DeOx temperatures

nGaAs ~800C TC
SI GaAs ~600 C pyro
nGaSb ~550 pyro
SI InP ~ 545 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.