2007 Fiscal Year Final Research Report Summary
Control of wave function coupling in stacked InAs quantum dots and its application to long-wavelength lasers
| Project/Area Number |
17560005
|
|---|
| Research Category |
Grant-in-Aid for Scientific Research (C)
|
| Allocation Type | Single-year Grants |
|---|
| Section | 一般 |
|---|
| Research Field |
Applied materials science/Crystal engineering
|
|---|
| Research Institution | The University of Tokyo |
|---|
Principal Investigator |
SAITO Toshio The University of Tokyo, Center for Collaborative Research, Research Associate (90170513)
|
|---|
| Co-Investigator(Kenkyū-buntansha) |
ARAKAWA Yasuhiko The University of Tokyo, Research Center for Advanced Science and Technology, Professor (30134638)
|
|---|
| Project Period (FY) |
2005 – 2007
|
| Keywords | semiconductor physics / quantum dots / InAs / wave functions / semiconductor lasers / semiconductor optical amplifier / light polarization / piezoelectric effect |
|---|
| Research Abstract |
We have theoretically studied the optical polarization in columnar InAs/GaAs quantum dots (QDs), in which the self-assembled QDs are vertically stacked with no interdot spacing. The model structure of the columnar QDs consists of truncated-cone-shaped InAs QDs with the stacking-layer numbers (SLNs) of 1, 3, 5, 7, and 9. We used the valence-force-field model to calculate the strain distribution. We find that the biaxial strain in the middle layers of the columnar QDs decreases with increasing SLN and becomes negative for SLN=9. This is due to the condition that the vertical lattice constant of InAs in these layers has to match that of the side GaAs. By using the strain-dependent 8-band kp theory for the electronic states, we calculated the transverse-electric(TE)- and transverse-magnetic(TM)-mode intensities for the electron-hole transitions. The piezoelectric effect is included in the calculations. For SLN=1 and 3, only the TE-mode transition occurs. With increasing SLN beyond 3, the TM-mode intensity increases while the TE-mode one decreases. Consequently, when SLN changes from 7 to 9, the dominant polarization character changes from the TE mode to the TM mode. This dominant polarization change is attributed to the increase of the light-hole character in the wave function of the ground hole state, which is the consequence of the negative biaxial strain in the middle layers for SLN=9. The change in the optical polarization calculated in this study is in good agreement with the photoluminescence experiment reported by Kita et al., Jpn. J. Appl. Phys., Part 2 41, L1143(2002).
|
Research Products
(15 results)
