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 7 nm, while 2DEG with of Ns∼2×1012 cm-2 remained for the TB=450 °C sample. Surface segregation of Si-sheet-doped (411)A InAlAs layers grown at TB was also characterized by secondary ion m- - ass spectrometry measurements. Si segregation length (λSi:1/e decay length of Si concentration) observed for TB=450 °C sample was 2.3 nm, which is 56% smaller than that for TB=540 °C (λSi=5.2 nm).