1. 05/05/28 Optical Characterization of Stem Well with Low Density Modulation-Doping
Toshiyuki Ihara
Abstract. I measured PL and PLE spectra of low density (4×1010cm-2) modulation doped stem well. I found that Indium annealing decreases the electron density in the stem well and 2D electron gas is NOT formed around Indium solder. This is a crucial problem for measurements of conductivity and for applying gate voltage of gated quantum structures.

2. Annealing of Indium solder on doped stem well
Low success rate for measurement of conductivity.
What is the origin of this difficulty?

3. PLE spectra measured at near/far from Indium solder
The electron density of stem well decreases by Indium annealing!?

4. PL scan near Indium solder
2D electron gas is NOT formed around Indium solder (width～10mm) .

5. Success rate of measurements of conductivity
0% when the etched depth is too large (>4.2mm)
30% when the etched depth is between 3.2 and 4.2 mm
(breakdown) 5% ohmic I-V line / 25% are schottky diode line.
Even if we obtain shot key diode line,
the gate structure might work when we apply large gate voltage

6. Next request
Please start the second growth of low density n-type doped T-wire with/without Carbon doping.
For the further investigation of Indium annealing effect on modulation doping, I request “modulation doped stem well with thin barrier (～1mm)”