You can see if your local pet supply store carries Zymox with cortisone. I've had good luck clearing up infections with that. You can read about it here
Last time I bought it http://www.amazon.com/ had the best price but shopping around is worthwhile.
I would also suggest trimming the hair on the underside of the ear so more air can circulate up under the heavy flap. You can trim any hair covering the ear opening too. Just be careful not to snip any ear while you do that.
This site goes over ear infection and has another ear cleaner mentioned that has had good results
here is just the product info
You can also fasten the ear flaps up over the head to let air in to help dry the ear which gives less opportunity for bacteria to grow.
You might try folding the ears open against the neck and use a toeless large man's athletic sock as a snood to hold the hears open so air can help dry any infection.
This can be a symptom of allergies in dogs. People use a snood with this breed to keep the ears out of the food dish too. The commercial snoods you see here usually cover the ear canal though
You can read about allergies and dermatitis in dogs here
Dogs can develop allergies to foods, and to inhaled items, and contact allergens such as rug cleaners, cedar beds, or chemicals including lawn chemicals or even flea bites.
You might want to try a different dog food that has no ingredients the same as what you feed now. Diets of Fish and Potato, venison, or rabbit etc. where the protein source is new and there are no grains in the food can work for many dogs for example. Another option is the hypoallergenic diet from your vet Hills ZD. Changing food does no good if you feed the same ingredients.
You might want to see if some plain Benadryl helps with any itching. A usual dose is 1mg per pound of dog. If you choose to use that please read here about cautions
Or you may want to consult with your vet and consider doing allergy testing.
This breed can also be prone to thyroid problems which can trigger allergies and infections. A vet can test for that issue too.
Hope this helps you!