Layers of InP:Tm, GaAs:Tm, GaP:Tm, and GaInP:Tm have been grown by metal-organic vapor phase epitaxy at atmospheric pressure using tris(isopropylcyclopentadienyl)thulium as a liquid Tm source. Electrical measurements revealed no characteristic influence of Tm on the electrical properties of the semiconductor host. Tm3+-related 4f emissions at 1.2 and 1.9 μm are observed both in GaAs and GaInP. In GaAs, the Tm3+ 4f luminescence at 1.2 μm consists of a series of very sharp lines. In GaInP samples, the Tm3+-related luminescence at 1.2 μm is much stronger than in the GaAs samples and is still observable at room temperature.

By photoluminescence and by Zeeman spectroscopy we study the characteristic 4f luminescence transition 3H5 → 3H6 at 1.0 eV of thulium in gallium arsenide which has been reported recently. It turns out that optically active Tm3+, which is present in mainly one specific type of center, does not occupy a simple substitutional lattice site. The results show a considerable tetragonal crystal field. The excitation mechanism of the 1.0-eV luminescence is investigated by photoluminescence excitation. The 3H5 → 3H6 is pumped most efficiently by trapping of free excitons.

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We present highly resolved photoluminescence studies on heat-treated nominally undoped InP, which was either unprotected or protected by SiO2 or Si3N4 caps during the annealing procedures. Annealing of InP above 350°C leads to six different sharp emissions in the wavelength range between 8790 and 8900 Å, which are not observed at 4 K in Zn-doped or Fe-doped samples. Based on temperature-dependent photoluminescence studies, time-resolved measurements and preliminary magnetic field studies we ascribe these emissions to isoelectronic bound exciton transitions. It is also shown that the two emissions at 8883 Å (11254 cm-1) (E) and 8889 Å (11246 cm-1) (F) belong to one center. We observe that the lines not only depend on the heat treatment but also on some unintentionally incorporated or residual impurities of a low concentration level. Possible candidates are discussed.