Single-electron capacitance spectroscopy of vertical quantum dots using a single-electron transistor

We have incorporated an aluminum single-electron transistor (SET) directly on top of a vertical quantum dot, enabling the use; of the SET as an electr ometer that is extremely responsive to the motion of charge into and out of the dot. Charge induced on the SET central island from single-electron add itions to the dot modulates the SET output, and we describe two methods for demodulation that permit quantitative extraction of the quantum dot capaci tance signal. The two methods produce closely similar results for the deter mined single-electron capacitance peaks. (C) 1999 American Institute of Phy sics. [S0003-6951(99)01404-7].