Compound Semiconductor Micro/Nanomechanical Devices

H. Yamaguchi and Y. Hirayama
Physical Science Laboratory

@Compound semiconductor heterostructures have been used in a wide variety of optical and electronic devices such as semiconductor lasers and ultra high-speed transistors, because their structure dimensions can be controlled down to the nanometer scale. In particular, functionalities based on quantum mechanical principles appear with structures that have dimensions comparable to electron waves. We integrate these "quantum structures" into microscopic mechanical structures in order to develop novel semiconductor devices. Figure 1 shows a scanning electron microscope (SEM) image of an InAs/AlGaSb displacement sensor that is an example of such a mechanical device fabricated from a compound semiconductor quantum structure. The single heterostructure consists of 15-nm-thick InAs and 285-nm-thick AlGaSb layers that were released from a GaAs (111)A substrate to form a cantilever beam by using photolithography and selective etching. The deflection of the cantilever can be detected from the change in resistance, for which we obtained a sensitivity as high as 0.01 nm/Hz0.5 [1]. Figure 2 shows the SEM image of another example, nanoscale InAs cantilevers, which were fabricated using a self-assembled growth technique. These have a thickness of 6-30 nm, a width of 20-100 nm, and a length of 50-500 nm. InAs has the unique property of electron surface accumulation, which enables us to fabricate conductive nanoscale cantilevers. It is expected that the energy of such a nanoscale cantilever is quantized at low temperatures and that such new quantum mechanical phenomena will bring about a revolution in the physics and technology of semiconductor fine structure devices.

[1] H. Yamaguchi, S. Miyashita, and Y. Hirayama, Appl. Phys. Lett. 82 (2003) 394.
[2] H. Yamaguchi and Y. Hirayama, Appl. Phys. Lett. 80 (2002) 4428.

Fig. 1. SEM image of fabricated InAs/AlGaSb displacement sensor.
Fig. 2. SEM image of nanoscale InAs cantilevers fabricated using a self-assemble growth technique.