docs: def GaP_Eg_Gamma(self, **kwargs):
      '''
      Returns the Gamma-valley bandgap, Eg_Gamma, in electron Volts at a
      given temperature, T, in Kelvin (default: 300 K).
  
      GaP has a unique Gamma-gap temperature dependence.
      '''
      T = kwargs.get('T', 300.)
      if T < 1e-4:
          return self.Eg_Gamma_0()
      return self.Eg_Gamma_0() + 0.1081 * (1 - 1. / tanh(164. / T))  # eV