Physics of Internal Photoemission and Its Infrared Applications in the Low-Energy Limit

Figure 2

(a) Schematic of different intervalence band optical transitions. (1)–(5) correspond to (1) direct transition; (2) direct transition + phonon emission (); (3) phonon absorption () + direct transition; (4) direct transition + phonon emission () (interband scattering); and (5) phonon absorption () + intraband photon absorption. Inset plots the optical processes taking place in an emitter(E)/barrier(B) heterojunction. (b) Optical absorption of -type GaAs. (c) Quantum yield spectra of different -type heterojunctions. Inset shows the flat-band (VB) diagrams [5] at zero bias. The doping concentrations are (A, B, and C) and (D). The vertical arrows indicate the features that remain the same in different samples.

(a)

(b)

(c)