Constant photocurrent method to probe the sub-bandgap absorption in wide bandgap semiconductor films : the case of α-Ga2O3

Nicol, David and Reynolds, Stephen and Barr, Kristopher and Roberts, Joseph W. and Jarman, John J. and Chalker, Paul R. and Massabuau, Fabien C.-P. (2024) Constant photocurrent method to probe the sub-bandgap absorption in wide bandgap semiconductor films : the case of α-Ga2O3. Physica Status Solidi B, 261 (5). 2300470. ISSN 0370-1972 (https://doi.org/10.1002/pssb.202300470)

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Abstract

The optical absorption coefficient is one of the fundamental properties of semiconductors and is critical to the development of optical devices. Herein, a revival of the constant photocurrent method is presented to measure sub-bandgap absorption in wide bandgap semiconductor films. The method involves maintaining a constant photocurrent by continually adjusting the impinging photon flux across the energy spectrum. Under such conditions, the reciprocal of the photon flux for uniformly absorbed light is proportional to the absorption coefficient. This method is applied to α-Ga 2O 3 and reveals that it can access the absorption coefficient from 1 × 10 5 cm −1 at the band edge (5.3 eV) to 0.8 cm −1 close to mid-bandgap (2.7 eV). Changes in the steepness of the absorption curve in the sub-bandgap region are in excellent agreement with defect states of α-Ga 2O 3 reported by deep level transient spectroscopy, indicating that the technique shows promise as a probe of energetically distributed defect states in thin film wide bandgap semiconductors.

ORCID iDs

Nicol, David, Reynolds, Stephen, Barr, Kristopher, Roberts, Joseph W., Jarman, John J., Chalker, Paul R. and Massabuau, Fabien C.-P. ORCID logoORCID: https://orcid.org/0000-0003-1008-1652;
  • Item type:Article
    ID code:88224
    Dates:
    Date
    Event
    1 May 2024
    Published
    27 February 2024
    Published Online
    15 February 2024
    Accepted
    Subjects:Science > Physics
    Department:Faculty of Science > Physics
    Depositing user: Pure Administrator
    Date deposited:19 Feb 2024 16:03
    Last modified:13 Nov 2024 01:23
    Related URLs:
    URI:https://strathprints.strath.ac.uk/id/eprint/88224
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