  We present a study on the intersublevel spacings of electrons and holes in a
single layer of InAs self-assembled quantum dots (SAQDs) using Fourier
transform infrared (FTIR) transmission spectroscopy without the application of
an external magnetic field. Epitaxial, complementary-doped and semi-transparent
electrostatic gates are grown within the ultra high vacuum conditions of
molecular beam epitaxy to voltage-tune the device, while a two dimensional
electron gas (2DEG) serves as back contact. Spacings of the hole sublevels are
indirectly calculated using the photoluminescence spectroscopy along with FTIR
spectroscopy. The observed spacings fit well to the calculated values for both
electrons and holes. Additionally, the intersubband resonances of the 2DEG are
enhanced due to the QD layer on top of the device.
