Optical detection of triplet excitons in GaS

Optically detected magnetic resonance has been used to investigate exciton recombination in the layered semiconductor GaS. Five triplet exciton resonances have been observed all with the same g-value of g_ex6 = 2.006 ± 0.002 but with different zero field splittings:

$\text{D}{}^{\mathrm{I}}\text{= + 0.013 cm}{}^{\mathrm{?1}}\text{, D}{}^{\mathrm{II}}\text{= + 0.024 cm}{}^{\mathrm{?1}}\text{, D}{}^{\mathrm{III}}\text{= + 0.025 cm}{}^{\mathrm{?1}}$

,

$\text{D}{}^{\mathrm{IV}}\text{= + 0.075 cm}{}^{\mathrm{?1}}\text{, D}{}^{\mathrm{V}}\text{= + 0.010 cm}{}^{\mathrm{?1}}$

. The resonances from the high energy wing are remarkably narrow and we believe that this may be the first observation of resonance from free indirect excitons.