Ga0.47In.53As/InP quantum well structures grown by atmospheric pressure organometallic vapor phase epitaxy are characterized by high‐resolution transmission electron microscopy (HRTEM) and 4 K photoluminescence (PL). Microdensitometer analysis of the HRTEM images shows GaInAs wells as narrow as 10 A˚ with slightly asymmetric interface widths. The InP to GaInAs transitions occur within 200 monolayers while the GaInAs to InP transitions are 3–5 monolayers wide, probably due to As carryover. 4 K PL shows half‐widths below 9 meV for quantization shifts up to 140 meV. PL peak shifts as large as 395 meV for the narrowest quantum wells are observed compared to bulk Ga0.47In0.53As.