Patent ID: 7115895

Claim:
Method for making a semiconductor heterostructure in a growth chamber ( 23 ) with gas inlet ( 26 , 30 ), comprising the steps: forming a virtual substrate on a silicon substrate ( 11 ; 51 ; 61 ), comprising a graded Si 1-x Ge x layer ( 12 ; 52 ; 62 ) followed by a Si 1-x Ge x layer ( 13 ; 53 ; 63 ) with constant concentration of Ge, using a high-density, low-energy plasma enhanced chemical vapor deposition (LEPECVD) process with i. a growth rate above 2 nm/s, ii. a substrate temperature between 400° and 850° C., and iii. a total reactive gas flow at the gas inlet between 5 sccm and 200 sccm, forming an active region ( 14 ; 58 ; 69 ) on said virtual substrate comprising a Ge-channel ( 55 ; 65 ) and a modulation-doped layer ( 56 ; 64 , 67 ) using a low-density, low-energy plasma enhanced chemical vapor deposition (LEPECVD) process by i. introducing hydrogen (H 2 ) into the growth chamber ( 23 ) to act as a surfactant, ii. maintaining a substrate temperature between 400° and 500° C., iii. introducing a dopant gas in a pulsed manner into the growth chamber ( 23 ) to provide for the modulation-doped layer ( 56 ; 64 , 67 ).