In the reverse active region of a BJT, equal doping of the emitter and collector can increase beta_r but is generally not recommended due to potential drawbacks. To enhance beta_f in forward active mode, the base region should be ultra-thin with light doping, achieving high injection efficiency, as seen in supergain devices with beta values around 5,000. However, this approach limits the Vce breakdown to a few volts and increases collector leakage current. For higher voltage capabilities, increasing base doping and thickness reduces beta_f but also decreases collector-base reverse leakage current. Higher beta_r can be achieved with light base doping and heavier collector doping, but this may negatively impact forward mode performance.