In this work, a systematic study for silicon doping of InGaAs via the metalorganic di‐tert‐butylsilane (DTBSi) as a non‐gaseous alternative to common gaseous precursors in a vertical close‐coupled showerhead metalorganic vapor phase epitaxy (MOVPE) reactor is conducted. At a growth‐temperature of 620 °C, doping concentrations up to n = 2.5 × 10 19 cm −3 and electron mobility up to μ n = 1831 cm 2 /Vs are achieved. It is found that, in the used reactor geometry, the doping process is mainly limited by the low decomposition of DTBSi, causing low incorporation efficiency compared to disilane. By increasing the reactor pressure from 100 to 200 mbar, it is possible to reduce the growth temperature by 40 K while achieving a doping concentration of n = 2.8 × 10 19 cm −3 with an electron mobility of μ n = 1631 cm 2 /Vs. A similar, although less pronounced effect can be observed when increasing the total carrier‐gas flow into the reactor. Increasing growth rate and V/III ratio are also found to enhance the dopant incorporation.