Welcome to Ishida Laboratory

Department of Electronics and Materials Science

Research : Semiconductor and quantum well physics

IV-VI compound semiconductor mid-infrared lasers

Physics of thermoelectric materials

1. The manuscript “Heat transport through propagon-phonon interaction in epitaxial amorphous-crystalline multilayers” by Takafumi Ishibe, Ryo Okuhata, Tatsuya Kaneko, Masato Yoshiya, Seisuke Nakashima, Akihiro Ishida, and Yoshiaki Nakamura was published in Communications Physics Vol.4, 153 (2021).

 

2. The manuscript “Landau level spectroscopy of PbSnSe topological crystal insulator”  by K.　K. Tikuisis, J. Wyzula, L. Ohnoutek, P. Cejpek, M. Hakl, C. Faugeras, K. Vyborny, A. Ishida, M. Veis, and M. Orlita was accepted in Physical Review B.

 

3. We derived a general formula for energy conversion efficiency of thermoelectric generator taking temperature dependent Seebeck coefficient, electrical resistivity, and thermal conductivity into account (J. Appl. Phys. 128, 135105 (2020))

The maximum conversion efficiency of thermoelectric materials is given by

where SH and SL are Seebeck coefficients at high and low temperature sides, and TH and TL are temperatures at high and low temperature sides, respectively. In the equation , other parameters were defined as follows:

                  

In the above equations, we defined average Seebeck coefficient, average thermal conductivity, and average resistivity as follows: 

                                      

 

4. We observed strong interband absorption in 7- 25 μm wavelength region from PbTe/PbSnTe-based type-II superlattice, which has potential application to long wavelength interband cascade lasers. 

5. We prepared optically pumped short-cavity PbSrS/PbS DH laser on Si substrate for single-mode tunable operation of 3 μm laser, which has future application to single-mode tunable diode lasers.  ( A. Ishida, et al., Appl. Phys. Lett. 111, 161104 (2017).)

6. Thermoelectric properties and thermoelectric conversion efficiencies of IV-VI semiconductors. Thermoelectric properties and conversion efficiency were calculated theoretically. (A. Ishida, et al., Materials Today Proc. 5, pp.10187-10194 (2018).)

   Seebeck coefficient and thermoelectric conversion efficiency of highly p-type PbTe were calculated considering heavy hole valleys along Σ axes, and the calculated results were compared with the theoretical data in the papers by Heremans et al. (Science 321, 554 (2008)), Y. Pei et al. (Nature 473, pp.66 (2011)), Zhang et al. ( JACS 134, pp.10031 (2012)), and J. Vineis, et al.(Phys. Rev. B 77, 235202(2008)), and good agreements were obtaind between theoretical and experimental values.

7. High efficiency and high power PbSrS/PbS MQW VECSEL (vertical external cavity surface emitting laser) was prepared on BaF₂(111) substrate, and the origin of high efficiency laser operation was clarified.