Gas source molecular beam epitaxial growth of GaP/AlP modulated superlattices and their optical properties

Abstract

GaP/AlP modulated superlattices: (GaP)m1(AlP)n1(GaP)m2(AlP)n2 superlattices (SLs) are grown on S-doped (001) GaP substrates by gas source molecular beam epitaxy (m = m1 + m2, n = n1 + n2, m1 ≥ m2, n1 ≥ n2). Blue shift of 4.2 K photoluminescence (PL) peak is observed with decreasing the period (m1 + n1) of the modulated SLs. Strong dependence of the PL intensity on the modulated SL structure is also observed. The modulated SLs of (m1 + n1 = odd, m2 + n2 = odd) periods have stronger PL intensities than those of (m1 + n1 = even, m2 + n2 = even) periods. It is also found that the PL intensity of the (odd, odd) modulated SLs ((9,4)(4,3) SL) shows slower temperature variation than that of the normal SLs ((13,7) SL). At 30 K, the PL intensity of the (9,4)(4,3) SL is 2500 times stronger than that of the (13,7) SL. Light emitting diodes having a normal SL ((13,7) SL) and a modulated SL ((9,4)(4,3) SL) as an active layer are fabricated. They exhibit room temperature electroluminescence (EL) at wavelength of ∼ 590 and ∼ 560 nm for the (13,7) normal SL and (9,4)(4,3) modulated SL light emitting diodes, respectively. The observed EL peak wavelengths are consistent with the PL peak wavelengths.