We present a vertical Ge quantum well (QW) asymmetric Fabry-Perot modulator design and integration scheme without distributed Bragg reflector (DBR). The field-dependent excitonic absorption and the modulator performance are calculated, showing the wide (20-nm-thick) well design gives a large absorption reduction for the normally-off modulator operation. For a 47 QW modulator, the theoretical contrast ratio exceeds 40 dB at 1 V and increases to 52.3 dB at 4 V bias with a 12.3-dB insertion loss and over-9-nm optical bandwidth (contrast>3dB). This robust DBR-free design can enable high-contrast-ratio Ge QW modulators.