Suppression of surface segregation of silicon dopants during molecular beam epitaxy of (411)A In[sub 0.75]Ga[sub 0.25]As∕In[sub 0.52]Al[sub 0.48]As pseudomorphic high electron mobility transistor structures

Abstract

The authors achieved considerable suppression of surface segregation of Si dopants in In0.75Ga0.25As∕In0.52Al0.48As high electron mobility transistor (HEMT) structures grown on (411)A InP substrates by molecular beam epitaxy (MBE). The (411)A HEMT structures were conventionally grown at a high substrate temperature (Ts) of 540°C in order to form the extremely flat (411)A heterointerfaces. This results in considerable surface segregation of Si dopants. Surface segregation of Si dopants was suppressed by lowering growth temperature of the top InAlAs barrier layer (TB) down to 450°C with keeping Ts of 540°C for other parts. Sheet carrier concentration (Ns) of two-dimensional electron gas (2DEG) was measured as a function of thickness (Lb) of the top InAlAs barrier for TB=450 and 540°C samples. Observed Ns of the TB=540°C sample vanished when Lb approached to 7nm, while 2DEG with of Ns∼2×1012cm−2 remained for the TB=450°C sample. Surface segregation of Si-sheet-doped (411)A InAlAs layers grown at TB was also ...