Piezo‐Phototronic Effect on Performance Enhancement of Anisotype and Isotype Heterojunction Photodiodes

Abstract

The piezo‐phototronic effect is confirmed as a promising methodology to optimize the performance of optoelectronic devices. However, not only positive effects, but also negative effects may be produced in some types of photodiodes (PDs) by the piezo‐phototronic effect, resulting in the restriction of the PDs' photoresponse performance enhancement. In order to obtain the largest possible photoresponse performance enhancement, it is essential to investigate how the piezo‐phototronic effect influences the photoresponse performance of PDs with different device configurations and structures. Here, the piezo‐phototronic effect on the photoresponse performance enhancement of anisotype (p‐Si/n‐ZnO) and isotype (n‐Si/n‐ZnO) heterojunction PDs is thoroughly investigated. The experimental results show that the piezo‐phototronic effect induced improvement of the p‐Si/n‐ZnO heterojunction PD is much larger than that of the n‐Si/n‐ZnO heterojunction PD. The energy band diagrams under compressive strains are carefully analyzed, revealing that two positive effects are introduced to the p‐Si/n‐ZnO heterojunction PD, whereas one positive and two negative effects are introduced to the n‐Si/n‐ZnO heterojunction PD by the piezo‐phototronic effect. This work presents an in‐depth understanding about the piezo‐phototronic effect on the photoresponse performances of PDs with different device configurations and structures.

On the Piezo‐Phototronic Effect in Si/ZnO Heterojunction Photodiode: The Effect of the Fermi‐Level Difference

“…But interestingly, the three kinds of p‐n junction PDs all present prominent photoresponse at −3 V, whereas the other two kinds of n‐n junction PDs both present obvious photoresponse at +3 V. These different photoresponse phenomena are caused by the different energy band configurations of the p‐n junction PDs and the n‐n junction PDs, which have been carefully analyzed in our previous work. [ 31 ] According to the experimental results, we put the p‐n junction and the n‐n junction PDs working under −3 V and +3V, respectively.…”

“…Table 1 shows the comparison of performance enhancement (i.e., the photoresponsivity) by the piezo‐phototronic effect in different kinds of ZnO‐based PDs [ 31,35,37–46 ] . Obviously, the enhanced magnitude of photoresponsivity in our device (i.e., p‐Si/n‐ZnO heterojunction PD with doping concentration of p‐Si is 1 × 10 18 cm −3 ) is larger than most of the other devices that have been reported.…”

“…[ 1–25 ] Nevertheless, due to the great differences in the energy band structures among different types of optoelectronic devices, the modulation effects in their energy bands are quite distinctive, resulting in different magnitude of their performances improvement. [ 29–32 ] Furthermore, not only positive effects, but also negative effects may be produced in some types of energy band structures, leading to the restriction or even the reduction of performance. [ 31–35 ] Figure presents the energy band structures of a p‐Si/n‐ZnO heterojunction photodiode and an n‐Si/n‐ZnO heterojunction photodiode (named as p‐n junction PD and n‐n junction PD in the following) as examples to illustrate the formation of the different modulation effects.…”

“…[ 29–32 ] Furthermore, not only positive effects, but also negative effects may be produced in some types of energy band structures, leading to the restriction or even the reduction of performance. [ 31–35 ] Figure presents the energy band structures of a p‐Si/n‐ZnO heterojunction photodiode and an n‐Si/n‐ZnO heterojunction photodiode (named as p‐n junction PD and n‐n junction PD in the following) as examples to illustrate the formation of the different modulation effects. Once the external compressive strain is applied to the PDs, positive piezo‐charges will be generated at the heterojunction interfaces.…”

“…In contrast to the p‐n junction PD, the piezo‐phototronic effect introduces one positive effect and one negative effect to the n‐n junction PD, which leads to the restriction or even the reduction of its performance, as shown in our previous work. [ 31 ] In summary, even in one type of optoelectronic device (Si/ZnO heterojunction PD as an example here) the differences in energy band structure can lead to different strain‐induced modulation effects, resulting in different performances enhancement. Therefore, for one type optoelectronic device we can modulate its energy band structure to optimize the performance modulation by the piezo‐phototronic effect.…”