Optical properties of InGaAsP quaternary quantum wells with Mn implantation

Full text: The controlled growth of semiconductor quantum wells with high optical quality has been achieved over a decade, and these heterostructures are present in several commercial devices such as semiconducting lasers, telecommunication devices and light detectors, among others. Recently, the new field of spintronics seeks for new materials that are suitable for controlling the spin degree of freedom for information transport and processing. One of the approaches devised to manipulate the carriers' spin is the addition of magnetic ions such as Manganese in conventional semiconductor materials. Efforts in this direction lead mostly to growth of diluted magnetic semiconductors such as MnAs or GaMnAs. In the present work we investigate an alternative way, and we report on the effects of Mn ion implantation on the optical properties of semiconductor quaternary quantum wells (QW) in order to assess its potential for spintronics. The samples consist of 40 nm InGaAsP quaternary QWs grown by metal-organic chemical vapor deposition on GaAs (001) substrates. Barriers and well alloy compositions were adjusted so that the QW emission lies close to 1.5 μ m (optical fiber transmission window). Mn ions were implanted at different doses (1, 10 and 20 at.%) and annealed at different temperatures (650 deg C or 750 deg C). An as-grown QW and a set of as-implanted samples were also available for comparison purposes. We performed low-temperature photoluminescence (PL) measurements and it was found that even after thermal treatment some of the samples did not recover from the usual damages induced by the ion implantation process. Samples treated at 650 deg C showed good recovery of substrate light emission efficiency, however the QW signal is not present, except for the sample with 20 at.% Mn implantation. The 750 deg C treatment led to better results since there is a presence of an emission band around 1050 nm. The best recover was found, again, for samples with 20 at.% Mn, which is intriguing. Usually one expects that a higher implantation doses would lead to an increased number of induced defects, thus making difficult the recovering of a good optical emission signal. In our case, surprisingly, the sample with highest Mn contents present the better PL spectrum. However the strong energy blue shift of PL peak, when compared to the non-implanted sample emission spectrum, might be related to a softening of quantum well interface due to thermal annealing. (author)