CATHODOLUMINESCENCE CHARACTERIZATION OF NITROGEN-DOPED ZNSE

Today nitrogen seems to be the most suitable acceptor for ZnSe-device applications. p-Type doping of ZnSe with nitrogen by metalorganic vapo ur phase epitaxy (MOVPE) is still not satisfactorily achieved. Stimula ted by the success of the plasma doping technique in MBE, a nitrogen p lasma source is used in order to overcome the well-known problem of lo w acceptor activation. In this work nitrogen-doped ZnSe layers were gr own by low-pressure MOVPE at growth temperatures of T-D= 320-480 degre es C from diethylzinc (DEZn) and diisopropylselenide (DIPSe) or ditert iarybutylselenide (DTBSe) on (100) GaAs substrates. The layer morpholo gy and luminescence properties of doped and undoped ZnSe layers were c haracterized by secondary electron (SE) imaging and panchromatic catho doluminescence (CL) imaging in order to investigate the influence of t he plasma source on the growth process. It is found that the layer mor phology is not deteriorated by the nitrogen dopant source. For monitor ing the dopant incorporation spectral cathodoluminescence measurements were performed at 14 K and at 77 K. Spectral CL measurements with foc ussed electron beam show that even with these fairly high excitation p ower densities (about 10 kW/cm(2)), donor-acceptor pair (DAP) luminesc ence is observed, which indicates the incorporation of a shallow accep tor at low growth temperatures T-D= 380 degrees C. Although there is e vidence for the incorporation of N by SIMS, it cannot be excluded that oxygen is also incorporated and contributes to the DAP luminescence. p-Type conductivity could not be demonstrated yet. The layers are high ly resistive.