The best way to operate a diode in the reverse-breakdown region in your circuit is by using a voltage regulator 1N5231A zener diode from Microsemi. Its maximum leakage current is 5 μA. Its maximum power dissipation is 500 mW. Its test current is 20 mA. It is made in a single configuration. This zener diode has an operating temperature range of -65 °C to 175 °C. This zener device has a nominal voltage of 5.1 V and a voltage tolerance of 10%.