**Author details**

noted an increase in the PZ field as the V/III ratio increases. It increases from 25.44

*Piezoelectric field dependence on the V/III ratio molar for (311) A (closed circles blue) and (311) B (closed*

**Samples Substrate orientation** *E***<sup>0</sup> (InP) (eV)** *Fint* **(KV/cm)** S1 (311) B 1.352 36.27 S1<sup>0</sup> (311) B 1.396 20.53 S1″ (311) B 1.361 8.11 S2 (311) A 1.351 25.44 S2<sup>0</sup> (311) A 1.349 32.86 S2″ (311) A 1.340 38.49

*Summary of energy gap (Eg) and the piezoelectric field (Fpz) values obtained from photoreflectance PR with*

From the surface kinetics aspect, it is possible to understand this difference in the variation of the PZ field with the V/III ratio for (311) A and (311) B orientation. The sign of the PZ charge is based on the atomic composition of the interfaces [38–40]. Therefore, it is necessary to distinguish between the substrates In planes, alluded to as (N11) A plane, and the planes P, alluded to as (N11) B-planes. The single-bond sites on a (311) surface are P sites and the double-bond sites are In locations. On the contrary, the surface (311) B has an inverse bonding arrangement as shown in **Figure 5** [5, 19]. Therefore, for (311) A-face, less As atoms appear to close the cultivated surface at a small V/III ratio. Because of the stronger bond strength of Al-As than In-As, additional As atoms bond to Al statistically, bringing about more AlAs. Therefore, when V/III decreases, the coefficient of incorporation decreases [5]. By contrast, if the V/III ratio increases, though the tendency of As to combining with Al is still high, because of this oversupply, In atoms have more opportunity to bond with As atoms. In this way, the In incorporation coefficient increases with V/III ratio [5], which creates an increase in the PZ field with V/III ratio for the (311) A-oriented

). Furthermore, we noted the opposite phenomenon of what is

occurring for (311) B-face. The PZ field in our samples cultivated on (311) A substrate

We plotted the type II transition energy with the field for both the A and B polarity substrates in order to estimate the role of the PZ field (see **Figure 11**). The

to 32.86 KV/cm when the V/III ratio increases almost twice [5].

samples (S2 and S2<sup>0</sup>

**188**

**Table 2.**

**Figure 11.**

*circles red) substrate orientation.*

*different V/III ratio molar.*

*Perovskite and Piezoelectric Materials*

has the opposite direction than for (311) B [5].

Badreddine Smiri\*, Faouzi Saidi and Hassen Maaref Laboratoire des Micro-optoélectroniques et Nanostructures, Faculté des Sciences Monastir, Université de Monastir, Monastir, Tunisia

\*Address all correspondence to: badreddinesmiri@gmail.com

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