Room-temperature photoreflectance characterization of pseudomorphic GaAlAs/InGaAs/GaAs high electron mobility transistor structures including the two-dimensional electron gas density

Abstract

Using contactless photoreflectance at 300K we have characterized three pseudomorphic GaAiAs/lnGaAs/GaAs high electron mobility transistor structures. The spectra from the InGaAs modulation-dop~ed quantum well (MDOW) channel can be accounted for on the basis of a step-like two-dimensional density of states (screened exciton) and a Fermi level filling factor. A detailed iineshape fit makes it possible to evaluate the Fermi energy, and hence the two-dimensional electron gas concentration. Furthermore, other important parameters of the system such as built-in electric fields, In composition and well width of the InGaAs MDOW channel can be evaluated.

Nondestructive evaluation of channel carrier concentration in modulation-doped InAlAs/InGaAs field-effect transistor structures by room-temperature photoluminescence

“…5 Raman scattering, 6 and the eddy current. 7 InAlAs/InGaAs HFET structures, however, usually contain an n ϩ contact InGaAs layer 8 on the InAlAs barrier layers for nonalloy ohmic contact because the quality of the structures is easily affected by thermal degradation, such as fluorine contamination, 9,10 during annealing in the alloy process.…”

<title>Characterization of semiconductor device structures by modulation spectroscopy</title>

“…1 lie on only one side of the baseline, with the exception of the highest lying sharp peak of sample #3, which is discussed in Ref. 11.…”

Electron density effects in the modulation spectroscopy of strained and lattice-matched InGaAs/InAlAs/InP high-electron-mobility transistor structures

“…2 ͑b͔͒. The details of the lineshapes contain information about the position of the Fermi level [2][3][4][5] relative to the bottom of the conduction subband associated with the optical transition under investigation. This may be used to estimate the electron population in the subband, as discussed in the following section.…”

“…1 In GaAs/AlGaAs modulation-doped field-effect transistors ͑MODFETs͒, the presence of a large signal from the GaAs buffer layer renders the analysis of the spectra difficult and inconclusive. 1 Our understanding of the electron density effects on the optical transitions has been substantially improved by studying the pseudomorphic AlGaAs/InGaAs/GaAs HEMT structure, [2][3][4][5] where the signals from the GaAs buffer and the two-dimensional electron gas in the active InGaAs channel are spectrally separated ͑by about 0.15 eV͒. While a theoretical analysis based on first principles is already available, 6 the dominant modulation mechanism remains an unresolved question.…”

“…While a theoretical analysis based on first principles is already available, 6 the dominant modulation mechanism remains an unresolved question. [2][3][4][5]7,8 A more thorough investigation must consider alternative heterostructures, for example, the In x Ga 1Ϫx As/In 0.52 Al 0.48 As/InP HEMTs, in order to ensure that the experimental and theoretical results are generally valid. The latter heterostructure offers the advantage of well-resolved phototransmittance signals in the InGaAs channel, with a negligible influence from the InP absorption edge due to a large ͑more than 0.6 eV͒ spectral separation.…”