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The thin strained superlattice (TSSL) concept is introduced as a means for extending the practical range of application for pseudomorphic Inx Ga1-x As on GaAs. Growth and characterization results are presented for pseudomorphic high electron mobility transistor structures with GaAs-In0.3 Ga0.7 As TSSL active layers grown by molecular beam epitaxy. The TSSLs are composed of three periods of GaAs(15 Å)- In0.3 Ga0.7 As(h2 ), where h2 ranges from 30 to 52 Å. Modulation doping of the TSSLs is provided by atomic planar-doped Al0.3 Ga0.7 As overlayers with 45 Å undoped spacers. 77 K Hall effect and transmission electron microscopy reveal that relatively thick TSSLs can be grown with high electronic and structural quality, comparable to much thinner In0.3 Ga0.7 As single quantum wells. Results are compared with a model for critical layer thickness and discussed in light of in situ reflection high-energy electron diffraction measurements. [ABSTRACT FROM AUTHOR]