Piezoelectric effects in III-V compound semiconductor tunneling devices

We show that piezoelectric effects can give rise to internal electric fields that modify the current-voltage characteristics of single barrier and double barrier resonant tunneling devices, if suitable stresses are applied.; For (111) oriented single barrier tunneling devices, asymmetric current shifts were observed under the stress along the (111) direction. For double barrier devices, we measured the current-voltage characteristics of (001) and (111)-oriented AlAs/GaAs/AlAs double barrier structures as a function of uniaxial, external stresses applied parallel to the (001), (110), (110) and (111) directions. The substrates were grounded in all measurements. Under the (001) stress, the I-V characteristics of (001)-oriented devices show symmetrical change, which can be explained by the deformation potential and the tunneling from {dollar}Gamma{dollar} to X valleys. Under the stress along (110) direction, the resonance peaks shift to more positive voltages for both positive and negative biases, while the peaks shift toward more negative voltages under the (110) stress. We also observed the peak shifts for (111)-oriented devices under the (111) stress. The shifts are similar to those (001) oriented devices under the (110) stress. All these asymmetric peak shifts are successfully explained by piezoelectric effects under uniaxial stresses.; We speculate that given proper optimization, this effect may lend itself to the implementation of novel devices that sense strain.; The growth conditions for single barrier and double barrier resonant tunneling devices on (001) and (111)B-oriented substrates were also studied, especially the growth conditions for devices on (111)B-oriented substrates. The quality of (111)-oriented devices is very sensitive to the growth conditions due to easily formed defects. As the results, we obtained high quality AlAs/GaAs/AlAs and AlGaAs/GaAs/AlGaAs double barrier resonant tunneling devices on (001)-oriented substrates as well as on (111)B-oriented substrates using a gas source molecular beam epitaxy(MBE) system. The (111)B-oriented device is believed to be the first successful resonant tunneling device grown in a gas source MBE system. The success is attributed to the use of misoriented substrates, suitable growth temperature, and precisely controlled Ga/As flux ratio.