Published: Feb. 17, 2017
  • K. Pollock, H. Q. Doan, C. Stanton, and T. Cuk
  • The Journal of Physical Chemistry听Letters.听2017, 8, 922. DOI: . Download

Figure 1. Schematic diagram of the sample with band diagram. The pump pulse (800 nm) excites from the back (n-GaAs) or the front (TMO or p-GaAs) side while the probe pulse records the change in reflectivity at the TMO and/or p-GaAs side. Inset: zoom on the pGaAs TMO interface. The probe beam reflects from the TMO/air, TMO/CLAP wave, and TMO/p-GaAs interfaces. 螖n refers to the CLAP-induced refractive index change in the TMO and p-GaAs.A prominent architecture for solar energy conversion layers diverse materials, such as traditional semiconductors (Si, III鈥揤) and transition metal oxides (TMOs), into a monolithic device. The efficiency with which photoexcited carriers cross each layer is critical to device performance and dependent on the electronic properties of a heterojunction. Here, by time-resolved changes in the reflectivity after excitation of an n-GaAs/p-GaAs/TMO (Co3O4, IrO2) device, we detect a photoexcited carrier distribution specific to the p-GaAs/TMO interface through its coupling to phonons in both materials. The photoexcited carriers generate two coherent longitudinal acoustic phonons (CLAPs) traveling in opposite directions, one into the TMO and the other into the p-GaAs. This is听the first time a CLAP is reported to originate at a semiconductor/TMO heterojunction. Therefore, these experiments seed future modeling of the built-in electric fields, the internal Fermi level, and the photoexcited carrier density of semiconductor/TMO interfaces within multilayered heterostructures.

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