Spin　photocurrent　spectra　induced　by　Rashba-　and　Dresselhaus-type　circular　photogalvanic　effect　(CPGE)　at　inter-band　excitation　have　been　experimentally　investigated　in　InGaAs/GaAs/AlGaAs　step　quantum　wells　(QWs)　at　room　temperature.　The　Rashba-　and　Dresselhaus-induced　CPGE　spectra　are　quite　similar　with　each　other　during　the　spectral　region　corresponding　to　the　transition　of　the　excitonic　state　1H1E　(the　first　valence　subband　of　heavy　hole　to　the　first　conduction　subband　of　electrons).　The　ratio　of　Rashba-　and　Dresselhaus-induced　CPGE　current　for　the　transition　1H1E　is　estimated　to　be　8.8±0.1,　much　larger　than　that　obtained　in　symmetric　QWs　(4.95).　Compared　to　symmetric　QWs,　the　reduced　well　width　enhances　the　Dresselhaus-type　spin　splitting,　but　the　Rashba-type　spin　splitting　increases　more　rapidly　in　the　step　QWs.　Since　the　degree　of　the　segregation　effect　of　indium　atoms　and　the　intensity　of　build-in　field　in　the　step　QWs　are　comparable　to　those　in　symmetric　QWs,　as　proved　by　reflectance　difference　and　photoreflectance　spectra,　respectively,　the　larger　Rashba-type　spin　splitting　is　mainly　induced　by　the　additional　interface　introduced　by　step　structures.　©　2014,　Yu　et　al.;　licensee　Springer.