I don't know much about on-chip signal generation but for the moment we are dealing with even shorter pulses generated with step recovery diode. It is in millimeter wave range, I don't know if this will help you.
you can consider using step recovery diode(SRD) to generate pulse with nanosecond pulse width with proper shaping circuitry, you can obtain subnanosecond pulse.
I would appreciate any references to publications detailing the step recovery diode(SRD) and pulse shaping circuitry techniques. I have been trying to locate these types of references for a while.
I recently research UWB pulse generation.You can use SRD and pulse shaping using RC filter.But its drawback is not be integrated.The attachment is about cmos/bicmos pulse generation circuit and based on 0.18 um process.