Probing the properties of self-organized InGaAs quantum dots on GaAs (311)B and (001) by conductive atomic force microscope tip

摘要

We have used conductive atomic force microscope (AFM) tips to study the electronic properties of self-organized InGaAs quantum dots (QDs) grown on GaAs (311)B substrate by atomic H-assisted molecular beam epitaxy. As shown previously, InGaAs QDs on GaAs (311)B surface exhibit a remarkably different self-organization characteristics compared to the QDs grown on (001) surface [cf. Appl. Phys. Lett. 73, 3411 (1998)]. A complex phase separation and strain-relief mechanism are believed to be responsible for the formation of high-density and well-ordered QDs arrays on (311)B surface, but the electronic structure of these QDs is not clearly understood at present. For this purpose, highly-doped Si AFM tips coated with a metal such as Au and Ti were used to measure the current-voltage (I-V) characteristics of QDs with varying sizes, and of any other arbitrary positions on the surface. In the case of QDs on (001) substrate, it was found that local surface potentials of larger QDs were smaller than small QDs possibly due to the effect of surface states. On the other hand, noticeable differences were not observed for QDs on (311)B with various sizes, which suggests that the local surface potential is nearly identical for each QD, and over the whole (311)B surface. Furthermore, a possible resonant tunneling behavior through the quantized energy levels was observed with a small QD with ～ 45 nm in diameter and ～ 4 om in height.