INVESTIGATIONS ON INDIUM-PHOSPHIDE GROWN BY CHEMICAL BEAM EPITAXY

In this paper, we present a systematic study of the properties of indi um phosphide (InP) layers grown by chemical beam epitaxy (CBE). Trimet hylindium (TMIn) and phosphine (PH3) are used as source materials. The relation between the phosphine cracker temperature and the cracking e fficiency has been studied by mass spectroscopy during growth. The gro wth rate and morphology of the layers have been studied by varying the TMIn and phosphine flow rates as well as the substrate temperature. W e have found that, under a wide range of growth conditions, the deposi tion rate is only determined by and proportional to the TMIn flow rate . This is in agreement with literature. Additionally, we observe that the growth rate decreases below a certain phosphine to TMIn flow rate (V/III) ratio and becomes phosphine flow limited. From investigations of the growth. rate as a function of temperature, it is concluded that the desorption of indium species from InP starts at a temperature sli ghtly below 540 degrees C. For this desorption process, we have found an activation energy of (217 +/- 20) kJ/mol. Further characterization of the InP layers has been carried out by photoluminescence and Hall m easurements. From both methods, the optimum growth conditions have bee n established. Under these conditions, we reproducibly obtain InP laye rs showing linewidths of the donor-bound exciton transition at 5K arou nd 0.25 meV and a mobility at 77K of about 7.0 . 10(4) cm(2)/Vs. From the analysis of the mobility in the temperature range from 20 to 300K, we conclude that, additionally to shallow donors and accepters, deep- donor centers with an activation energy of about 150 meV are present i n all layers.