The impact of strain-balancing quantum dot superlattice arrays is critical to device performance. InAs/GaAs/GaP strain-balanced quantum dot arrays embedded in p-i-n diodes were investigated via high resolution x-ray diffraction (HRXRD) and photoluminescence (PL) as a function of the GaP thickness. A three-dimensional modification of the continuum elasticity theory was proposed and an optimal thickness was determined to be 3.8 ML. HRXRD-determined in-plane strain in superlattices with this range of GaP thickness gave an empirical value for the GaP thickness to be 4.5 ML. Optical characterization indicated the highest integrated PL intensity for the sample at the optimal strain balanced condition.