Were you thinking of a mercury vapor bulb? A halogen bulb doesn't produce heat differently than other incandescent bulbs would. There are halogen "flood" style bulbs and "spot" style bulbs. The flood produces a wider beam of warmth/light. I use these rather than the spot, which has a tighter beam. I feel the flood gives the cham a bit more choice in how close it can perch to bask. A tight spot may force the cham to sit directly under it to get the heat.