1. 05/07/18 Optical Characterization of High-Mobility Quantum Well with Low-density Modulation-Doping Toshiyuki Ihara Abstract. I measured PL and PLE spectra of high-mobility 33nm quantum well with low-density modulation doping. The sample 03-11-05.1 contains 2D electron gas (2DEG) of 5.9x10 10 cm -2 without parallel conduction. On the contrary, the sample 03- 24-05.3 contains 2DEG of 3.5x10 10 cm -2 with parallel conduction. The decrease of the 2D electron density due to Indium solder is clearly observed PL scan of 03-24-05.3, where the exciton peak appears at low electron density. The PLE spectra depends on the sample and also on the position (near / far from In solder). We need further investigation to know which is the main origin that causes the spectral differences, the electron density or the parallel conduction.

2. Sample information Sample name03-11-05.103-24-05.3 LP Quantum well 330 Å GaAs Barrier10% AlGaAs Si doping3x10 11 cm -2 (7.4A x 11sec) Set back 800 Å 1500 Å Electron density5.9x10 10 cm -2 3.5x10 10 cm -2 Parallel conductionnoyes Indium annealing30s ※ ‘LP’ means ‘Low density’ & ‘Parallel conduction’

3. PL scan near Indium solder The decrease of 2D electron density around Indium solder is clearly observed in low-density doped quantum well (03-24-05.3 LP).

4. PLE spectra of both samples What causes the difference of PLE spectra, the electron density or parallel conduction?

5. PLE spectra measured near / far from In solder Though there are interesting differences, the mechanism is still unclear…

6. Measurements of conductivity There are two problems: ① Resistance is large. ② Success rate is low. Further investigation is needed (shorter annealing time, use InSb etc.) …To be continued